Non-aqueous electrolyte secondary battery and method for manufacturing the same

ABSTRACT

To provide a structure which allows production of an electrode, even if the film thickness of an electrode is increased; and a non-aqueous electrolyte secondary battery using the same. 
     A non-aqueous electrolyte secondary battery including a power generating element including: two electrodes having different polarity and formed by forming an active material layer on a current collector; and an electrolyte layer positioned between the electrodes, wherein at least one of the active material layers of the two electrodes having different polarity contains an active material and a conductive member made from an electron conducting material, the active material layer has a first principal surface which comes into contact with the electrolyte layer side, and a second principal surface which comes into contact with the current collector side, at least a part of the conductive member forms a conductive path electrically connecting the first principal surface to the second principal surface, and the conductive path is in contact with the active material in the periphery of the conductive path, at least a part of the surface of the active material is coated with a coating agent that includes a coating resin and a conduction assisting agent, and an electrolyte solution contained in the electrolyte layer or the two electrodes having different polarity is a gel phase electrolyte.

TECHNICAL FIELD

The present invention relates to a non-aqueous electrolyte secondarybattery and a method for manufacturing the same.

BACKGROUND ART

Recently, there has been a strong demand for a reduction in carbondioxide emissions in order to have environmental protection. Theautomobile industry expects that the introduction of electric vehicles(EV) or hybrid electric vehicles (HEV) will lead to a reduction incarbon dioxide emissions. Thus, intensive efforts are being made todevelop a motor driving secondary battery which holds the key to thepractical application of those electric vehicles. As for the secondarybattery, attention is drawn to a lithium ion secondary battery which canachieve high energy density and high output density.

Recently, the use of various electric vehicles has been promoted withthe expectation of solving environmental/energy issues. A secondarybattery is being developed intensively as a vehicle-mounted powersource, such as a motor driving power source, which holds the key to thewidespread use of these electric vehicles. However, in order to ensurewidespread use, it is necessary to increase the performance and reducethe cost of batteries. In addition, with an electric vehicle, it isnecessary to bring the single-charge driving distance closer to that ofa gasoline engine vehicle. Thus, batteries with higher energy densityare in demand. In order for batteries to have a high energy density, itis necessary to reduce as much as possible battery members that are notdirectly related to a battery reaction. As a battery which allows savingof current collecting tab of a battery single cell or bus bar forconnection between single cells, has very high volume efficiency, and issuitable for mounting in vehicles, a bipolar type secondary battery hasbeen suggested. In a bipolar type secondary battery (also referred to asbipolar secondary battery), a bipolar type electrode in which a positiveelectrode is formed on one surface of a current collector and a negativeelectrode is formed on the other surface of a current collector is used.Furthermore, it has a structure in which plural bipolar electrodes arelayered such that the positive electrode and negative electrode can faceeach other while being mediated by a separator containing an electrolytelayer. Accordingly, the bipolar type secondary battery forms one batterycell (i.e., single battery) consisting of a current collector, apositive electrode and a negative electrode present between currentcollectors, and a separator (i.e., electrolyte layer). Furthermore, forthe purpose of having even higher performance, use of a resin in which aconductive filler is dispersed in a current collector has beensuggested.

For a lithium ion secondary battery with the aforementionedconstitution, high energy density is important as a basic characteristicin order to have storage of energy that is required for runningautomobiles. As a method for increasing the energy density of a battery,a method in which ratio of a positive electrode material and a negativeelectrode material within a battery is increased is known. In PatentLiterature 1, a means for increasing energy density of a battery bylowering the relative ratio of a current collector or a separator isdisclosed.

CITATION LIST Patent Literatures

Patent Literature 1: JP 9-204936 A

SUMMARY OF INVENTION Technical Problem

As described in Patent Literature 1, it is believed that havingincreased film thickness of an electrode may lead to reduction ofrelative ratio of a current collector or a separator and is effectivefor increasing the energy density.

However, according to a conventional method of applying slurry of anactive material on a current collector to increase the film thickness ofan electrode, there has been a case in which manufacture of an electrodeitself becomes difficult.

As such, it is necessary to create a structure which still allowsmanufacture of an electrode even when the film thickness of an electrodeis increased.

Solution to Problem

The inventors of the present invention conducted intensive studies tosolve the problems described above.

As a result, by having, as a constitutional member of an electrode, afirst principal surface which comes into contact with an electrolytelayer side, and a second principal surface which comes into contact witha current collector side, and by including a conductive member whichforms a conductive path in contact with an active material andelectrically connecting the first principal surface to the secondprincipal surface, a thick electrode can be manufactured.

Namely, provided is a non-aqueous electrolyte secondary battery in whichat least one of the electrodes contains a conductive member and anactive material coated with a coating agent that includes a coatingresin and a conduction assisting agent and the conductive member forms aconductive path which is in contact with an active material andelectrically connects both principal surfaces. Accordingly, it was foundthat the aforementioned problems can be solved, and the presentinvention is completed.

Effect of Invention

According to the invention, by including a conductive member which formsa conductive path in contact with an active material and electricallyconnecting the first principal surface to the second principal surface,a non-aqueous electrolyte secondary battery with increased electrodefilm thickness can be achieved.

Furthermore, the electrolyte of the non-aqueous electrolyte secondarybattery of the present invention is gellated. Thus, even under increasedvibration, an influence of gellation is low so that the constitutionalmember of an electrode can be stably maintained. As a result, the cyclecharacteristics are also improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating a bipolarsecondary battery as one embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating an enlargedpart of an encircled portion in FIG. 1.

FIG. 3 is a cross-sectional view schematically illustrating only apositive electrode active material layer illustrated in FIG. 2.

FIG. 4 is a cross-sectional view schematically illustrating otherexemplary embodiment of the positive electrode active material layer.

FIG. 5 is a cross-sectional view schematically illustrating otherexemplary embodiment of the positive electrode active material layer.

FIG. 6 is a cross-sectional view schematically illustrating otherexemplary embodiment of the positive electrode active material layer.

FIG. 7 is a cross-sectional view schematically illustrating otherexemplary embodiment of the positive electrode active material layer.

FIG. 8 is a process flow chart schematically illustrating the process offilling an active material in voids of a structural body.

FIG. 9 is a process flow chart schematically illustrating the process offixing the active material and a conductive member on top of a film.

FIG. 10 is a process flow chart schematically illustrating the processof fixing the active material and the conductive member using a resin.

FIG. 11 is a perspective view illustrating an outer appearance of a flatlithium ion secondary battery, which is a representative embodiment of asecondary battery.

DESCRIPTION OF EMBODIMENTS

Provided by one embodiment of the present invention is a non-aqueouselectrolyte secondary battery having a power generating elementincluding two electrodes having different polarity and formed by formingan active material layer on a current collector; and an electrolytelayer placed between the electrodes in which at least one of the activematerial layers of the two electrodes having different polarity containsan active material and a conductive member made from an electronconducting material, and the active material layer has a first principalsurface which comes into contact with the electrolyte layer side, and asecond principal surface which comes into contact with the currentcollector side, at least a part of the conductive member forms aconductive path electrically connecting the first principal surface tothe second principal surface, and the conductive path is in contact withthe active material in the periphery of the conductive path, at least apart of the surface of the active material is coated with a coatingagent that includes a coating resin and a conduction assisting agent,and the electrolyte solution contained in the two electrodes havingdifferent polarity or the electrolyte layer is a gel phase electrolyte.

According to the present invention, by including a conductive memberwhich forms a conductive path in contact with an active material andelectrically connecting the first principal surface to the secondprincipal surface, a non-aqueous electrolyte secondary battery withincreased electrode film thickness can be provided.

Furthermore, the electrolyte solution of the non-aqueous electrolytesecondary battery of the present invention is gellated. As there is agellated electrolyte, a homogenous electrode reaction can be obtainedwithout having any deformation even when certain force is appliedlocally on an electrode, and it leads to an improvement of the cyclecharacteristics.

Hereinbelow, embodiments of the present invention are explained indetail in view of drawings, but the technical scope of the presentinvention shall be defined by the description of the claims and it isnot limited to the following embodiments. Furthermore, the dimensionalratio in the drawings is exaggerated for the sake of convenience ofexplanation, and it may be different from the actual ratio.

Furthermore, in the present specification, the bipolar lithium ionsecondary battery may be simply referred to as a “bipolar secondarybattery”, and an electrode for a bipolar lithium ion secondary batterymay be simply referred to as a “bipolar electrode”. Furthermore, theterm referred to as an “active material” may mean any one of a positiveelectrode active material and a negative electrode active material, orboth of them. The same shall apply to an “active material layer”. Thosecan be reasonably interpreted by a person skilled in the art.

<Bipolar Secondary Battery>

FIG. 1 is a cross-sectional view which schematically illustrates abipolar secondary battery as one embodiment of the present invention. Abipolar secondary battery 10 illustrated in FIG. 1 has a structure inwhich an approximately rectangular power generating element 21, in whicha charging and discharging reaction actually occurs, is sealed inside alaminate film 29 as a battery outer casing material.

As illustrated in FIG. 1, the power generating element 21 of the bipolarsecondary battery 10 of this embodiment has plural bipolar electrode 23in which a positive electrode active material layer 13 electricallybound on one surface of a current collector 11 is formed and a negativeelectrode active material layer 15 bound on the other surface of acurrent collector 11 is formed. Each bipolar electrode 23 is laminatedvia an electrolyte layer 17 to form the power generating element 21.Furthermore, the electrolyte layer 17 has a constitution in which anelectrolyte is supported in planar center part of a separator as asubstrate. In that case, the bipolar electrode 23 and the electrolytelayer 17 are alternately laminated such that the positive electrodeactive material layer 13 of one bipolar electrode 23 and the negativeelectrode active material layer 15 of the other bipolar electrode 23which is adjacent to said one bipolar electrode 23 can face each othervia the electrolyte layer 17. Namely, it is an arrangement in which theelectrolyte layer 17 is inserted between the positive electrode activematerial layer 13 of one bipolar electrode 23 and the negative electrodeactive material layer 15 of the other bipolar electrode 23 which isadjacent to said one bipolar electrode 23.

The adjacent positive electrode active material layer 13, theelectrolyte layer 17, and the negative electrode active material layer15 form one single battery layer 19. Thus, it can be said that thebipolar secondary battery 10 has a constitution in which the singlebattery layer 19 is laminated. In addition, on outer periphery of thesingle battery layer 19, a seal part (i.e., insulating layer) 31 isdisposed. Accordingly, liquid junction caused by leakage of anelectrolyte solution from the electrolyte layer 17 is prevented, contactbetween neighboring current collector 11 in a battery or an occurrenceof short circuit resulting from subtle displacement of an end part ofthe single battery layer 19 in the power generating element 21 isprevented. Furthermore, only on a single surface of the outermost layercurrent collector 11 a on the positive electrode side which is presenton the outermost layer of the power generating element 21, the positiveelectrode active material layer 13 is formed. Furthermore, only on asingle surface of the outermost layer current collector 11 b on thenegative electrode side which is present on the outermost layer of thepower generating element 21, the negative electrode active materiallayer 15 is formed.

Furthermore, in the bipolar secondary battery 10 illustrated in FIG. 1,a positive electrode current collecting plate 25 is disposed such thatit can be adjacent to the outermost layer current collector 11 a on thepositive electrode side, and it is extended and drawn from the laminatefilm 29 as a battery outer casing material. Incidentally, a negativeelectrode current collecting plate 27 is disposed such that it can beadjacent to the outermost layer current collector 11 b on the negativeelectrode side, and it is also extended and drawn from the laminate film29 as a battery outer casing material.

The number of times of laminating the single battery layer 19 isadjusted depending on desired voltage. Even for the bipolar secondarybattery 10, to prevent environmental deterioration and impact fromoutside at the time of use, it is preferable to have a structure inwhich the power generating element 21 is sealed under reduced pressurein the laminate film 29 as a battery outer casing material, and thepositive electrode current collecting plate 25 and the negativeelectrode current collecting plate 27 are drawn to the outside of thelaminate film 29. Furthermore, although embodiments of the presentinvention are explained herein by using a bipolar secondary battery asan example, type of a non-aqueous electrolyte battery to which thepresent invention can be applied is not particularly limited, and anapplication can be made to any non-aqueous electrolyte secondary batteryknown in the art such as so-called parallel lamination type battery inwhich a power generating element is composed of single battery layersthat are connected to each other in parallel.

Hereinbelow, explanations are given for main constitutional elements ofthe bipolar secondary battery of this embodiment.

[Current Collector]

The current collector has a function of mediating electron transfer fromone surface in contact with a positive electrode active material layerto the other surface in contact with a negative electrode activematerial layer. The material for forming a current collector is notparticularly limited, but a metal or a resin with conductivity can beadopted.

Specific examples of the metal include aluminum, nickel, iron, stainlesssteel, titanium, and copper. In addition to them, a clad material ofnickel and aluminum, a clad material of copper and aluminum, or aplating material of a combination of those metals can be preferablyused. It can be also a foil obtained by coating aluminum on a metalsurface. Among them, from the viewpoint of electroconductivity orpotential for operating a battery, aluminum, stainless steel, copper,and nickel are preferable.

As for the latter resin with conductivity, a resin formed by aconductive polymer material or a non-electron conductive polymermaterial optionally added with a conductive filler can be mentioned.Examples of the electroconductive polymer material include polyaniline,polypyrrole, polythiophene, polyacetylene, polyparaphenylene,polyphenylenevinylene, polyacrylonitrile, polyoxadiazole and the like.These electroconductive polymer materials have sufficientelectroconductivity even if an electroconductive filler is not added,and therefore, they are advantageous in terms of facilitatingmanufacturing process or of reducing weight of the current collector.

Examples of the non-electroconductive polymer material includepolyethylene (PE; high density polyethylene (HDPE), low densitypolyethylene (LDPE), etc.), polypropylene (PP), polyethyleneterephthalate (PET), polyethernitrile (PEN), polyimide (PI),polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE),styrene-butadiene rubber (SBR), polyacrylonitrile (PAN),polymethylacrylate (PMA), polymethylmethacrylate (PMMA), polyvinylchloride (PVC), polyvinylidene fluoride (PVdF), polystyrene (PS) and thelike. Such non-electroconductive polymer materials may have excellentvoltage resistance or solvent resistance.

To the above-mentioned electroconductive polymer materials or to thenon-electroconductive polymer materials, if necessary, anelectroconductive filler can be added. In particular, when a resin to bea base material of the current collector includes only anon-electroconductive polymer, an electroconductive filler isindispensable in order to give electroconductivity to the resin.

As the electroconductive filler, any material can be used if it haselectroconductivity, without particular limitation. For example, as amaterial excellent in electroconductivity, potential resistance, orlithium ion shielding characteristics, a metal, an electroconductivecarbon or the like can be mentioned. As the metal, although there is noparticular limitation, it is preferable to contain at least one metalselected from the group including Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn,In, and Sb, or an alloy or metal oxide containing these metals. Further,as the electroconductive carbon, although there is no particularlimitation, it is preferably one containing at least one kind selectedfrom the group including acetylene black, VULCAN, BLACK PEARL, carbonnanofiber, Ketjen black, carbon nanotube, carbon nanohorn, carbonnanobaloon and fullerene.

The addition amount of the electroconductive filler is not particularlylimited, if it can give sufficient electroconductivity to the currentcollector, and generally, it is around 5 to 35% by mass.

Furthermore, the current collector of this embodiment may have a singlelayer structure composed of a single material or a laminate structure inwhich layers composed for those materials are suitably combined.Furthermore, from the viewpoint of blocking the transfer of lithium ionsbetween single battery layers, it is possible to form a metal layer onpart of the current collector.

[Positive Electrode Active Material Layer, Negative Electrode ActiveMaterial Layer]

According to the embodiment of the present invention, at least one ofthe positive electrode active material layer and negative electrodeactive material layer includes a conductive member composed of electronconducting material and an active material. In this embodiment, at leasta part of the surface of the active material is coated with a coatingagent that includes a coating resin and a conduction assisting agent.Furthermore, according to the embodiment of the present invention, theactive material layer has a first principal surface which comes intocontact with the electrolyte layer side, and a second principal surfacewhich comes into contact with the current collector side. Furthermore,at least a part of the conductive member forms a conductive pathelectrically connecting the first principal surface to the secondprincipal surface.

The embodiment of the present invention includes an exemplary case inwhich the conductive member is a conductive fiber consisting part ofnon-woven fabric, an exemplary case in which the conductive member is aconductive fiber consisting part of woven or knitted fabric, anexemplary case in which the conductive member is a conductive fiberdispersed between the first principal surface and the second principalsurface, and an exemplary case in which the conductive member is aconduction-treated resin consisting part of a foamed resin.

First, by using a drawing, explanations are given for an example inwhich the conductive member is a conductive fiber consisting part ofnon-woven fabric.

FIG. 2 is a cross-sectional view schematically illustrating the enlargedpart of the encircled portion in FIG. 1.

As illustrated in FIG. 2, it has a structure in which the single batterylayer 19 is sandwiched by two pieces of the current collector 11.

The positive electrode active material layer 13 has a sheet shape withpre-determined thickness of t1, and it is provided with a firstprincipal surface 111 disposed on the electrolyte layer 17 side and asecond principal surface 121 disposed on the current collector 11 side.The positive electrode active material 14 is included in the positiveelectrode active material layer 13. In this embodiment, the positiveelectrode active material 14 is coated with a coating agent, andexplanations therefor will be given later.

Similar to the above, the negative electrode active material layer 15has a sheet shape with pre-determined thickness of t2, and it isprovided with a first principal surface 211 disposed on the electrolytelayer 17 side and a second principal surface 221 disposed on the currentcollector 11 side. The negative electrode active material 24 is includedin the negative electrode active material layer 15. In this embodiment,the negative electrode active material 24 is coated with a coatingagent, and explanations therefor will be given later.

It is preferable that the thickness t1 of the positive electrode activematerial layer 13 and the thickness t2 of the negative electrode activematerial layer 15 are, each independently, 150 to 1500 μm. When theelectrode is thick like that, a large amount of the active material canbe included in a battery, a battery with high capacity can be prepared,and it is effective for increasing the energy density. The thickness t1is more preferably 200 to 950 μm, and even more preferably 250 to 900μm. The thickness t2 is more preferably 200 to 950 μm, and even morepreferably 250 to 900 μm. According to the characteristic structure ofthe present invention, an electrode with such thickness can be achieved,and it is effective for increasing the energy density.

FIG. 3 is a cross-sectional view schematically illustrating only apositive electrode active material layer illustrated in FIG. 2.

As illustrated in FIG. 3, a positive electrode active material layer 100is provided with the first principal surface 111 and the secondprincipal surface 121 (not illustrated in the drawing). Furthermore,between the first principal surface 111 and the second principal surface121, a conductive fiber 131 as a conductive member and a positiveelectrode active material 14 as an active material are included.

According to the embodiment illustrated in FIG. 3, the conductive memberis a conductive fiber 131 which forms part of non-woven fabric. Becausethere are many voids in a non-woven fabric, an electrode can be formedby filling the active material 14 in the voids. Filling the voids withcoated active material will be described later in detail.

In the conductive fiber 131, an end part on one side of part of thefiber reaches the first principal surface 111 and an end on the otherside reaches the second principal surface 121. Consequently, at least apart of the conductive fiber 131 forms a conductive path whichelectrically connects the first principal surface 111 to the secondprincipal surface 121.

Furthermore, between the first principal surface 111 and the secondprincipal surface 121, many conductive fiber 131 are present inentangled state. However, even for a case in which the plural conductivefiber 131 are in contact with one another to yield continuous connectionfrom the first principal surface 111 to the second principal surface121, it can be said that the conductive fiber forms a conductive pathwhich electrically connects the first principal surface 111 to thesecond principal surface 121.

In FIG. 3, an example of the conductive fiber 131 which corresponds to aconductive path electrically connecting the first principal surface 111to the second principal surface 121 is illustrated. The fiberrepresented by the conductive fiber 131 a is an example in which oneconductive fiber serves as a conductive path while the two fibersrepresented by the conductive fiber 131 b are an example in which twoconductive fibers serve as a conductive path as they are in contact witheach other.

Examples of the conductive fiber include carbon fiber such as PAN carbonfiber and pitch carbon fiber, conductive fiber containing a highlyconductive metal or graphite uniformly dispersed in synthetic fiber,metal fiber obtained by converting metals such as stainless steel intofiber, conductive fiber containing organic fiber whose surface is coatedwith a metal, and conductive fiber containing organic fiber whosesurface is coated with a resin containing a conductive substance. Amongthese conductive fibers, carbon fiber is preferred.

In the present embodiment, the conductive member preferably has anelectrical conductivity of 50 mS/cm or more. The electrical conductivitycan be determined by measuring the volume resistivity in accordance withJIS R 7609 (2007) “Carbon fiber—Method for determination of volumeresistivity” and calculating the reciprocal of the volume resistivity.As the electrical conductivity is 50 mS/cm or more, the conductive pathsthat are formed of the conductive fiber and connect the first principalsurface 111 to the second principal surface 121 have small electricalresistance and allow smooth transfer of electrons from the activematerial far from the current collector, and therefore desirable.

The conductive fiber preferably has an average fiber diameter of 0.1 to20 μm. The fiber diameter of the conductive fiber is measured by SEMobservation. The average fiber diameter of the conductive fiber isdetermined as follows. Ten conductive fibers are randomly selected in a30 μm-square field of view. The diameter at or near the middle of eachof the ten fiber is measured. This measurement is performed at threefields of view. The average of the diameters of a total of 30 fibers istaken as the measured value.

The fiber length of the conductive fiber is not particularly limited.

In the present embodiment, the active material is a coated activematerial in which part of the surface of the material is coated with acoating agent 151 that includes a coating resin and a conductionassisting agent 16. Details will be described later.

The conductive paths formed of the conductive fiber 131 are in contactwith the positive electrode active material 14 around the conductivepaths. Such contact of the conductive paths with the positive electrodeactive material allows the electrons generated from the positiveelectrode active material particles to quickly reach the conductivepaths and flow through the conductive paths to the current collector.Since the conductive paths are formed of the conductive member that isan electron conductive material, electrons can smoothly reach thecurrent collector. In the present embodiment, the active material is acoated active material. However, even in a case in which the coatingagent is in contact with a conductive path, the conductive path can beregarded as being in contact with the active material.

In an active material layer without such a conductive path, electronshave to pass through an active material, which is not highlyelectronically conductive, and thus they are less likely to smoothlyreach the current collector. Furthermore, in a case in which electronsare conducted via a conduction assisting agent consisting ofparticulates, there is electrical resistance between the particles.Thus, since the particles of the conduction assisting agent are notcontinuously joined to one another, electrons unavoidably pass throughregions with high electrical resistance. Electrons are thus less likelyto smoothly reach the current collector.

Furthermore, in the foregoing description, the movement of electrons isdescribed referring to a case in which electrons generated from thepositive electrode active material flow to the current collector.However, electrons flowing from the current collector to the positiveelectrode active material can also pass through conductive paths andsmoothly reach the positive electrode active material. That is, the sameeffects can be obtained in charging and discharging.

The conduction assisting agent 16 is selected from materials withconductivity. Details of the conduction assisting agent will bedescribed later. Further, in the present embodiment, the conductionassisting agent 16 is contained in the coating agent 151, but it may bein contact with the positive electrode active material 14. If theconduction assisting agent 16 is contained in the coating agent 151 orin contact with the positive electrode active material 14, electronconductivity from the positive electrode active material 14 to arrivalat the conductive path can be further enhanced.

Regarding the embodiment of FIG. 3, explanations are given by having apositive electrode as an example. However, in the case of a negativeelectrode, a negative electrode active material may be used as an activematerial instead of a positive electrode active material. Details of thenegative electrode active material will be also described later.

Also in the negative electrode, the conductive path is in contact withnegative electrode active material around the conductive path. As in thecase of the positive electrode, electrons generated from the negativeelectrode active material quickly reach the conductive path and passthrough the conductive path smoothly to the current collector.Similarly, electrons flowing from the current collector to the negativeelectrode active material can smoothly reach the negative electrodeactive material.

FIG. 4 is a cross-sectional view schematically illustrating otherexemplary embodiment of the positive electrode active material layer.

In the positive electrode active material layer 100 of the embodimentillustrated in FIG. 4, the conductive member is a conductive fiber 113which constitutes part of a woven fabric. The woven fabric is composedof warp yarns 113 a and weft yarns 113 b formed of the conductive fiber.The positive electrode active material layer 100 according to theembodiment illustrated in FIG. 4 has the same configuration as thepositive electrode active material layer 100 according to the embodimentillustrated in FIG. 2, except that a fabric-form fiber structurecorresponding to the non-woven fabric in FIG. 3 is a woven fabric. Themethod for weaving a woven fabric is not particularly limited, andexamples of the usable woven fabrics include those woven by plainweaving, twill weaving, satin weaving, or pile weaving. It is alsopossible to use, instead of a woven fabric, a knitted fabric composed ofa conductive fiber. Furthermore, the method for knitting a knittedfabric is not particularly limited, and examples of the usable knittedfabrics include those knitted by weft knitting, warp knitting, orcircular knitting. Similar to the non-woven fabric, the woven fabric andthe knitted fabric have many voids between the conductive fibersconstituting them. As such, an electrode (active material layer) can beformed by filling the voids with a coated active material.

Furthermore, at least a part of the conductive fiber 113 has a portionextending to the first principal surface 111 and another portionextending to the second principal surface 121. Thus, at least a part ofthe conductive fiber 113 forms a conductive path that electricallyconnects the first principal surface 111 and the second principalsurface 121.

Other constitutions including type of preferred conductive fiber andtype of preferred active material are the same as those of theembodiment illustrated in FIG. 2, and thus the detailed explanationtherefor is omitted here. Furthermore, by having a negative electrodeactive material as the active material, a negative electrode can beprepared.

FIG. 5 is a cross-sectional view schematically illustrating otherexemplary embodiment of the positive electrode active material layer.

In a positive electrode active material layer 100 according to theembodiment illustrated in FIG. 5, the conductive member is a conductivefiber 213 dispersed between the first principal surface 111 and thesecond principal surface 121. The conductive fiber 213 is not part of astructural body formed of conductive fiber, such as the non-wovenfabric, the woven fabric, or the knitted fabric illustrated in FIG. 3and FIG. 4. The method for manufacturing a positive electrode activematerial layer of the embodiment illustrated in FIG. 5 will be describedlater in detail. According to the embodiment, production is made byusing a slurry containing the conductive fiber and the coated activematerial, in which the conductive fibers are dispersed in the activematerial layer, and it should not be regarded as one in which voidsamong fibers are filled with a coated active material.

At least part of the conductive fiber 213 has a portion extending to thefirst principal surface 111 and another portion extending to the secondprincipal surface 121. In other words, at least a part of the conductivefiber 213 forms a conductive path that electrically connects the firstprincipal surface 111 to the second principal surface 121.

In FIG. 5, the fiber represented by the conductive fiber 213 a is anexample in which one conductive fiber serves as a conductive path whilethe two fibers represented by the conductive fiber 213 b are an examplein which two conductive fibers serve as a conductive path as they are incontact with each other.

Other constitutions including type of preferred conductive fiber andtype of preferred active material are the same as those of theembodiment illustrated in FIG. 2, and thus the detailed explanationtherefor is omitted here. Furthermore, by having a negative electrodeactive material as the active material, a negative electrode can beprepared.

In the embodiment illustrated in FIG. 5, the conductive fiber as theconductive member and the coated active material may be fixed onto afilm such that the fixed shape can be retained loosely to the extentthat they do not flow. If the film is made of a material having highconductivity (conductive material), the film can be used as a currentcollector. In addition, the conductivity is not inhibited even if thefilm contacts with a current collector, and therefore desirable. It isnoted that the film is not illustrated in FIG. 5. The production methodin which the conductive fiber as the conductive member and the coatedactive material are fixed onto the film will be described later indetail.

In another separate embodiment, the conductive fiber as the conductivemember and the coated active material may be fixed by a resin to keepthe conductive fiber dispersed in the active material in a lithium ionbattery.

FIG. 6 is a cross-sectional view schematically illustrating otherexemplary embodiment of the positive electrode active material layer.

The positive electrode active material layer 100 of the embodimentillustrated in FIG. 6 has the same constitution as that according to theembodiment illustrated in FIG. 5 except that the conductive fiber 213 asthe conductive member and positive electrode active material 14 (coatedactive material) as the active material are fixed by a resin 214.

Examples of the resin include vinyl resins, urethane resins, polyesterresins, and polyamide resins.

The production method in which a conductive fiber as conductive memberand a coated active material are fixed by a resin will be explainedlater in detail.

FIG. 7 is a cross-sectional view schematically illustrating otherexemplary embodiment of the positive electrode active material layer.

In the embodiments illustrated in FIG. 7, the conductive member is aresin 313 prepared by conduction treatment and constituting a part of afoamed resin. The foamed resin has many voids. As such, an electrode canbe formed by filling the voids with a coated active material.

The resin prepared by conduction treatment may be, for example, a resinprovided with conductivity obtained by forming a conductive thin film onthe surface of a resin, or a resin provided with conductivity obtainedby mixing a resin with a conductive filler such as a metal or carbonfiber. The resin itself may be a conductive polymer or a resin in whichthe conductive polymer is further provided with conductivity.

Examples of a method for forming a conductive thin film on the surfaceof a resin include metal plating, a deposition treatment, or asputtering treatment.

In the embodiment illustrated in FIG. 7, the resin 313 provided withconductivity is continuous from the first principal surface 111 to thesecond principal surface 121. The resin 313 provided with conductivityforms a conductive path that electrically connects the first principalsurface 111 to the second principal surface 121.

The foamed resin including the resin provided with conductivity ispreferably a resin foam, such as a polyurethane foam, a polystyrenefoam, a polyethylene foam, or a polypropylene foam. In particular, thefoamed resin is preferably a polyurethane foam whose surface is platedwith a metal such as nickel.

In a preferred embodiment of the present invention, if the conductivemember is a foamed resin including a resin provided with conductivity,the foamed resin including a resin provided with conductivity preferablyhas an electrical conductivity of 100 mS/cm or more. The electricalconductivity of the foamed resin can be determined by the four-terminalmethod. As the foamed resin including a resin provided with conductivityhas an electrical conductivity of 100 mS/cm or more, the conductivepaths that are formed of the conductive fiber and connect the firstprincipal surface to the second principal surface have small electricalresistance. This advantageously enables smooth transfer of electronsfrom the active material far from the current collector, and thereforedesirable. Furthermore, by having a negative electrode active materialas the active material, a negative electrode can be prepared.

In the positive electrode active material according to a preferredembodiment of the present invention, including the embodimentsillustrated in FIGS. 3 to 7, the proportion by volume of the conductivemember is preferably 0.1 to 15% by volume based on the volume of thepositive electrode active material layer. In other words, the volume ofthe conductive member in the positive electrode active material layer ispreferably relatively small. A small volume of the conductive memberindicates that voids not occupied by the conductive member can be filledwith a large number of coated active materials. By filling the voidswith a large number of coated active materials, an electrode with highcapacity can be obtained. Furthermore, in the present example, theproportion by volume of the conductive member is about 2% by volume.

Furthermore, in a preferred embodiment of the present invention, theproportion by volume of the coated active material is preferably 30 to80% by volume based on the volume of the active material layer. As theproportion of the coated active material is large, the electrode canhave high capacity. Furthermore, in the present example, the proportionby volume of the conductive member is about 46% by volume.

Explanations are further given regarding the method for manufacturing anon-aqueous electrolyte secondary battery according to a preferredembodiment of the present invention.

The method for manufacturing a non-aqueous electrolyte secondary batteryaccording to a preferred embodiment of the present invention is a methodfor manufacturing a non-aqueous electrolyte secondary battery having apower generating element including two electrodes having differentpolarity and formed by forming an active material layer on a currentcollector; and an electrolyte layer placed between the electrodes, inwhich at least one of the active material layers of the two electrodeshaving different polarity contains an active material and a conductivemember made from an electron conducting material, and the activematerial layer has a first principal surface which comes into contactwith the electrolyte layer side, and a second principal surface whichcomes into contact with the current collector side, at least a part ofthe conductive member forms a conductive path electrically connectingthe first principal surface to the second principal surface, and theconductive path is in contact with the active material in the peripheryof the conductive path, at least a part of the surface of the activematerial is coated with a coating agent that includes a coating resinand a conduction assisting agent, and the electrolyte solution containedin the two electrodes having different polarity or the electrolyte layeris a gel phase electrolyte.

Regarding the method for manufacturing a non-aqueous electrolytesecondary battery according to this embodiment, explanations are givenfirst for the method for producing an electrode (active material layer)based on several separate modes.

One mode of the producing an electrode (active material layer) of thenon-aqueous electrolyte secondary battery of the present inventionincludes a step of preparing a structural body which includes aconductive member, has plural voids therein, and is provided with thefirst principal surface and the second principal surface, a step ofapplying the first principal surface or the second principal surface ofthe structural body with a slurry containing the coated active material,and a step of filling the voids of the structural body with the coatedactive material under increased or reduced pressure.

The production method of the above mode is suitable for producing anactive material layer of a mode which has been explained in view of FIG.3, FIG. 4, or FIG. 7.

First, a structural body which includes a conductive member, has pluralvoids therein, and is provided with the first principal surface and thesecond principal surface is prepared (i.e., the structural body becomesa skeleton of the first principal surface and the second principalsurface of an active material layer).

The structural body which may be used is preferably a non-woven fabricincluding the conductive member made of conductive fiber, a woven fabricor knitted fabric including the conductive member made of conductivefiber, or a foamed resin including the conductive member made of a resinprovided with conductivity. The descriptions of the non-woven fabric,woven fabric, knitted fabric, and foamed resin are the same as thosedescribed in the above, and thus are omitted here.

FIGS. 8(a) and 8(b) illustrate a step of filling voids in a structuralbody with coated active material. These figures illustrate an embodimentin which a non-woven fabric is used as a structural body.

Next, a slurry containing the coated active material is applied to thefirst principal surface or the second principal surface of thestructural body.

The active material is coated by a coating agent to yield a coatedactive material. The method for producing a coated active material willbe described later.

The slurry containing the active material may be either a solvent slurrycontaining a solvent or an electrolyte solution slurry containing anelectrolyte solution. Furthermore, the explanations regarding the slurrycan be also applied to other embodiments.

Examples of the solvent include water, propylene carbonate,1-methyl-2-pyrrolidone (N-methyl pyrrolidone), methyl ethyl ketone,dimethyl formamide, dimethyl acetamide, N,N-dimethylaminopropylamine,and tetrahydrofuran.

Furthermore, as an electrolyte solution, an electrolyte solutioncontaining supporting salts and/or organic solvent, which is used formanufacture of a lithium ion battery, can be used. As for the supportingsalts, those generally used for manufacture of a lithium ion battery canbe used, and as for the organic solvent, those generally used for anelectrolyte solution can be used. Meanwhile, the electrolyte solution tobe contained in the electrode or the electrolyte layer needs to begellated by a gelling agent. Furthermore, the supporting salts andorganic solvent may be used either singly or in combination of two ormore types thereof.

The slurry is prepared by dispersing a coated active material, and ifnecessary, a conduction assisting agent to a concentration of 5 to 60%by weight based on the weight of a solvent or an electrolyte solutionfollowed preparing them in a slurry.

The slurry containing the coated active material can be applied to thefirst principal surface or the second principal surface of thestructural body using any coating device like a bar coater and a brush.

FIG. 8(a) schematically illustrates a slurry applied to a secondprincipal surface of a non-woven fabric as a structural body. A slurrycontaining the positive electrode active material 14, which is obtainedby coating with a coating agent 151, is applied to a second principalsurface 62 of a non-woven fabric 60.

Subsequently, the voids in the structural body are filled with thecoated active material by pressurization or depressurization.

The pressurization may be performed by pressing from above the coatingsurface with the slurry using a pressing machine. The depressurizationmay be performed by suction using a vacuum pump with filter paper ormesh in contact with the surface of the structural body to which theslurry is not applied.

Because the structural body has voids, by the pressurization ordepressurization, the voids in the structural body can be filled withthe coated active material,

FIG. 8(a) shows an arrow indicating the direction of pressurization fromabove a coating surface with a slurry and an arrow indicating thedirection of depressurization from below filter paper 70. FIG. 8(b)illustrates the positive electrode active material layer 100 in whichvoids in the structural body are filled with the coated active material.The positive electrode active material layer 100 illustrated in FIG.8(b) is the same as the positive electrode active material layer 100illustrated in FIG. 3.

If the slurry containing the coated active material is a solvent slurrycontaining a solvent, a step of distilling the solvent is furtherpreferably performed thereafter.

Furthermore, if the slurry containing the coated active material is anelectrolyte solution slurry containing an electrolyte solution, thevoids in the structural body are fully filled with the coated activematerial and the electrolyte solution. Such a configuration ispreferable as an electrode for lithium ion batteries. Meanwhile, theelectrolyte solution to be contained in the electrode or the electrolytelayer needs to be gellated by a gelling agent.

Also in a case in which the structural body is not a non-woven fabricbut a woven fabric or knitted fabric containing the conductive member ora foamed resin including a resin provided with conductivity, an activematerial layer can be produced by filling the coated active materialinto the voids in the structural body by the above step.

Another aspect of the present invention includes a step of applying aslurry containing the conductive member and the coated active materialto a film and a step of fixing the coated active material and conductivemember on a film under pressurization or depressurization.

The method according to this aspect is suitable for producing thepositive electrode active material layer according to the embodimentwhich has been explained by using FIG. 5.

FIGS. 9(a) and 9(b) schematically illustrate a step of fixing the coatedactive material and conductive member onto a film.

First, the slurry containing a conductive member 213, and a coatedactive material, which is a positive electrode active material 14obtained by coating with a coating agent 151 containing a coating resinand a conduction assisting agent 16, is applied on a film 470.

The slurry may be, for example, a slurry obtained by further adding anddispersing conductive fiber as the conductive member into the slurrydescribed above.

The conductive fiber may be any of the conductive fiber described in theabove. As for the shape of the conductive fiber, the conductive fiber ispreferably independent from one another. They preferably do not have athree-dimensional structure such as a non-woven fabric, a woven fabric,or a knitted fabric. If conductive fibers are independent from oneanother, the fiber is dispersed in the slurry.

In this embodiment, the slurry may be an electrolyte solution slurrycontaining an electrolyte solution. The electrolyte solution which isthe same as the electrolyte solution for the electrolyte solution slurrydescribed above can be used. The slurry may be a solvent slurrycontaining a solvent. Meanwhile, the electrolyte solution to becontained in the electrode or the electrolyte layer needs to be gellatedby a gelling agent.

The film 470 is preferably a film capable of separating the coatedactive material and the conductive member from the electrolyte solutionand the solvent in the subsequent pressurization or depressurizationstep. If the film is made of a material having high conductivity(conductive material), the film can substitute for the currentcollector. In addition, the conductivity is not inhibited even if thefilm contacts with the current collector, and therefore desirable. Forexample, a material with an electrical conductivity of 100 S/cm or morecan be suitably used. Examples of materials with such properties whichcan be used include filter paper containing conductive fiber such ascarbon fiber and metal mesh. Those can be used as a current collector.

The metal mesh which may be used is preferably made of stainless steelmesh. Examples of such a metal mesh include SUS316-made twilled Dutchweave wire mesh (available from Sunnet Industrial Co., Ltd.). The metalmesh preferably has an opening size that does not allow the coatedactive material or the conductive member to pass through the mesh. Forexample, a metal mesh of 2300 mesh is preferably used.

In the present embodiment, the slurry can be applied to the film withany coating device like a bar coater and a brush.

FIG. 9(a) schematically illustrates a slurry applied to a film. A slurrycontaining the coated active material and conductive fiber 213 isapplied to a filter paper 470 as a film.

Next, the coated active material and the conductive member are fixedonto the film by pressurization or depressurization.

The pressurization or the depressurization can be performed in the samemanner as in the step described above. By the pressurization ordepressurization, the electrolyte solution or the solvent is removedfrom the slurry, and the conductive fiber as the conductive member andthe coated active material are fixed onto the film such that the fixedshape is retained loosely to the extent that they do not flow.

FIG. 9(b) illustrates a positive electrode active material layer 110 inwhich the conductive fiber 213 as the conductive member and the coatedactive material are fixed on the filter paper 470.

If the film in the positive electrode active material layer 110 is madeof a conductive material, the film can substitute for a currentcollector. Alternatively, the film and a current collector may bebrought into contact so that they can serve as one current collector.Accordingly, a second principal surface 121 in the positive electrodeactive material layer 110 can be defined as a portion in which theconductive fiber 213 as the conductive member contact with the filterpaper 470.

If the film is made of a non-conductive material, the film is preferablydisposed on the separator side. Alternatively, the film may be used as aseparator. Examples of the film made of a non-conductive materialinclude an aramid separator (manufactured by Japan Vilene Company,Ltd.).

Furthermore, in the present embodiment, if the slurry is an electrolytesolution slurry containing an electrolyte solution, the film ispreferably a film impermeable to the coated active material butpermeable to the electrolyte solution, and the electrolyte solution ispreferably allowed to pass through the film by pressurization ordepressurization so as to be removed.

It is also preferable that a press step of pressurizing the slurry at ahigher pressure is performed.

In the press step, the pressure difference is greater than that in thepressurization or depressurization in previous step in order to improvethe density of the coated active material. The press step has a conceptwhich encompasses both pressurization in a case in whichdepressurization is performed in previous step and pressurization at ahigher pressure in a case in which pressurization is performed inprevious step.

Pressure for the press step can be suitably set, but it is preferably 1to 5 kg/cm² or so, for example.

Furthermore, by performing a step of transferring the coated activematerial fixed onto the film to a principal surface of a currentcollector or a separator so as to arrange a first principal surface ofthe active material layer on the principal surface of the separator orproduce an electrode having a second principal surface of the activematerial layer on the principal surface on the current collector.

Regarding the transferring step, it is preferable that the transfer iscarried out by bringing a principal surface opposite the film intocontact with a principal surface of a current collector or a separator.

If the film is made of a conductive material and the film is used as acurrent collector, the transfer is preferably carried out by bringing aprincipal surface opposite the film into contact with a principalsurface of a separator. Furthermore, if the film is not used as acurrent collector, a step of removing the film is preferably performedafter carrying out the transfer. Alternatively, the film may be used aspart of a separator.

FIGS. 10(a) and 10(b) schematically illustrate a step of fixing thecoated active material and conductive member using a resin.

First, a composition for active material containing the conductivemember, coated active material, and resin is prepared.

As for the conductive member, similar to the embodiment which has beenexplained in view of FIGS. 9(a) and 9(b), it is preferable to use theconductive fiber having a shape in which each fiber is independent fromone another.

Preferred examples of the resin include vinyl resins, urethane resins,polyester resins, and polyamide resins. These resins are preferred fromthe viewpoint of moldability.

In the composition for an active material, the resin may be in the formof a resin solution dissolved in a solvent or in the form of solid, suchas a pellet that is fluidized when heated.

Furthermore, the resin may be a coating resin which is included in acoating agent.

In the composition for an active material, if the resin is present inthe form of a resin solution having a resin dissolved in a solvent, theconductive member and the active material are preferably dispersed inthe resin solution. Also in a case in which the resin is in the form ofsolid, the resin, the conductive member, and the active material arepreferably dispersed, not localized in a particular part.

The composition for an active material thus prepared is hot-pressed sothat the conductive member and the active material are fixed by theresin.

The method for hot-press is not particularly limited. For example, amethod in which the composition for an active material containing acoated active material, a conductive fiber 213, and a resin 214 isapplied to a plate 570 such as a metal plate illustrated in FIG. 10(a)followed by hot-press from the upper surface can be mentioned.

The composition for an active material may be applied by any applicationdevice like a bar coater and a brush. The hot-pressing may be performedusing a usual hot-pressing device.

Furthermore, in a case in which the resin is the resin for coating thecoated active material, when the conductive member and the coated activematerial are applied to a plate and hot-pressed, the conductive memberand the (coated) active material are fixed by coating resin melted byheat.

The active material fixed by the coating resin may be coated activematerial that remains coated with the coating resin or may be activematerial from which the coating has been somewhat peeled off.

The conditions for the hot-pressing may be determined according to thecuring conditions of the resin to be used and are not particularlylimited. For a urethane resin, for example, the hot-pressing ispreferably performed at 100° C. to 200° C. and 0.01 to 5 MPa for 5 to300 seconds. For a vinyl resin, the hot-pressing may be performed at 80°C. to 180° C. and 0.01 to 5 MPa for 5 to 300 seconds.

According to hot-pressing, as illustrated in FIG. 10(b), a positiveelectrode active material layer 110 in which the conductive fiber 213and the coated active material are fixed by a resin 214 can be produced.

(Positive Electrode Active Material)

Examples of the positive electrode active material 14 include complexoxides of lithium and transition metals (e.g., LiCoO₂, LiNiO₂, LiMnO₂and LiMn₂O₄), transition metal oxides (e.g., MnO₂ and V₂O₅), transitionmetal sulfides (e.g., MoS₂ and TiS₂), and conductive polymers (e.g.,polyaniline, polyvinylidene fluoride, polypyrrole, polythiophene,polyacetylene, poly-p-phenylene, and polycarbazole)

(Negative Electrode Active Material)

Examples of the negative electrode active material 24 include graphite,amorphous carbon, calcined products of polymer compounds (e.g., productsobtained by calcining and carbonizing phenolic resins or furan reins),cokes (e.g., pitch coke, needle coke, petroleum coke), carbon fiber,conductive polymers (e.g., polyacetylene, polypyrrole), tin, silicon,and metal alloys (e.g., lithium-tin alloy, lithium-silicon alloy,lithium-aluminum alloy, lithium-aluminum-manganese alloy).

(Coating Agent)

As described above, according to an embodiment of the present invention,at least one of the positive electrode active material layer and thenegative electrode active material layer includes a conductive materialcomposed of an electron conducting material and an active material.According to this embodiment, at least a part of the surface of theactive materials is coated with a coating agent 151 including a coatingresin and a conduction assisting agent 16.

(Conduction Assisting Agent)

The conduction assisting agent 16 is selected from materials withconductivity.

Specific examples thereof include, but not limited to, metals [e.g.,aluminum, stainless steel (SUS), silver, gold, copper, titanium], carbon[e.g., graphite, carbon blacks (acetylene black, Ketjen black, furnaceblack, channel black, thermal lamp black)], and mixtures thereof.

These conduction assisting agents may be used either singly or two ormore thereof may be used in combination. Alloys or metal oxides thereofmay be used. From the viewpoint of the electrical stability, aluminum,stainless steel, carbon, silver, gold, copper, titanium, and mixturesthereof are preferred, silver, gold, aluminum, stainless steel, andcarbon are more preferred, and carbon is still more preferred. Theconduction assisting agent may be a particulate ceramic material orresin material coated with a conductive material (any of the metalsmentioned above as conductive materials) by plating, for example.

Shape (form) of the conduction assisting agent is not limited to aparticle form, and it may be the form other than particle form or theform like carbon tube or the like which is available as a so-calledfilter type conductive resin composition.

From the viewpoint of the electric characteristics of a battery, theaverage particle diameter (i.e., primary particle diameter) of aconduction assisting agent is preferably 0.01 to 10 μm, although it isnot particularly limited thereto. Furthermore, in the presentspecification, the “particle diameter” means the maximum distance Lamong the distances between any two points on a contour of a conductionassisting agent. Values of “average particle diameter” indicate thevalues that are determined by using an observation means like scanningtype electron microscope (SEM) or a transmission type electronmicroscope (TEM) and calculating the average value of particle diameterof particles that are observed from several to several tens of fields ofview.

(Coating Resin)

According to a preferred embodiment of the present invention, the resinfor coating an active material (hereinbelow, also simply referred to asa “coating resin”) has tensile elongation at break of 10% or higher in asaturated liquid absorption state.

The tensile elongation at break in a saturated liquid absorption statecan be measured as follows: the coating resin is punched into a dumbbellshape; the dumbbell-shaped coating resin is immersed in an electrolytesolution at 50° C. for 3 days so as to have the coating resin in asaturated liquid absorption state; and the tensile elongation at breakis measured according to ASTM D683 (specimen's shape: Type II). Thetensile elongation at break is the rate of elongation until the testspecimen breaks in a tensile test as calculated by the followingformula:Tensile elongation at break (%)=[(Length of test specimen atbreak−Length of test specimen before test)/Length of test specimenbefore test]×100

When the tensile elongation at break of a coating resin is 10% or morein a saturated liquid absorption state, the coating resin has adequateflexibility, so that it is possible to alleviate the volume change ofthe electrode and suppress expansion of the electrode according tocoating with an active material. The tensile elongation at break is morepreferably 20% or more, and even more preferably 30% or more.Furthermore, the upper limit value of the tensile elongation at break ispreferably 400%, and more preferred upper limit value is 300%.

Furthermore, a urethane resin obtained by reacting an active hydrogencomponent with an isocyanate component is also preferred as a coatingresin. Because the urethane resin has flexibility, it is possible toalleviate the volume change of the electrode and suppress expansion ofthe electrode according to coating the active material of a lithium ionbattery with a urethane resin.

According to a preferred embodiment of the present invention, thecoating resin has a liquid absorption rate of 10% or more when immersedin an electrolyte solution and has a tensile elongation at break of 10%or more in a saturated liquid absorption state.

The liquid absorption rate when immersed in an electrolyte solution canbe determined by measuring the weight of the coating resin before andafter immersion in the electrolyte solution and using the followingformula.Liquid absorption rate (%)=[(Weight of coating resin after immersion inelectrolyte solution−Weight of coating resin before immersion inelectrolyte solution)/Weight of coating resin before immersion inelectrolyte solution]×100

The electrolyte solution to be used to determine the liquid absorptionrate is an electrolyte solution in which LiPF₆ as an electrolyte isdissolved to a concentration of 1 mol/L in a mixed solvent in whichethylene carbonate (EC) and diethyl carbonate (DEC) are mixed in avolume ratio (EC:DEC) of 3:7.

To determine the liquid absorption rate, the coating resin is immersedin the electrolyte solution at 50° C. for 3 days. The coating resin willbe in saturated liquid absorption state after being immersed in theelectrolyte solution at 50° C. for 3 days. The expression “saturatedliquid absorption state” refers to the state in which the weight of thecoating resin does not increase anymore even if the coating resin isimmersed in the electrolyte solution for a longer time.

As the liquid absorption rate is 10% or more, the electrolyte solutionis sufficiently absorbed in the coating resin, and lithium ions caneasily pass through the coating resin, so that the movement of lithiumions between the active material and the electrolyte solution is nothindered. The liquid absorption rate is preferably 20% or more, morepreferably 30% or more. Furthermore, the upper limit value of the liquidabsorption rate is preferably 400%, more preferably 300%.

The conductivity of lithium ions in the resin for coating an activematerial of an embodiment of the present invention can be determined bymeasuring, according to an alternating current impedance method, theconductivity of the coating resin at room temperature after the coatingresin is set in saturated liquid absorption state.

The conductivity of lithium ions determined by the above method ispreferably 1.0 to 10.0 mS/cm. With the conductivity in this range, thelithium ion battery can exhibit sufficient performance.

Furthermore, according to another embodiment, the coating resin ispreferably a urethane resin having a liquid absorption rate of 10% ormore when immersed in an electrolyte solution and having a tensileelongation at break of 10% or more in a saturated liquid absorptionstate, in which the urethane resin is obtained by reacting an activehydrogen component with an isocyanate component.

The active hydrogen component preferably contains at least one selectedfrom the group consisting of polyether diols, polycarbonate diols, andpolyester diols.

Examples of polyether diols include polyoxyethylene glycol (hereinbelow,abbreviated as “PEG”), polyoxyethylene oxypropylene block copolymerdiol, polyoxyethylene oxytetramethylene block copolymer diol; ethyleneoxide adducts of low molecular weight glycols such as ethylene glycol,propylene glycol, 1,4-butane diol, 1,6 hexamethylene glycol, neopentylglycol, bis(hydroxymethyl)cyclohexane, and4,4′-bis(2-hydroxyethoxy)-diphenyl propane; condensed polyether esterdiol obtained by reaction of PEG having a number average molecularweight of 2,000 or less with at least one dicarboxylic acid [such asaliphatic dicarboxylic acids having a carbon number of 4 to 10 (e.g.,succinic acid, adipic acid, and sebacic acid) and aromatic dicarboxylicacids having a carbon number of 8 to 15 (e.g., terephthalic acid andisophthalic acid)]; and mixtures of two or more thereof.

In a case in which polyether diol contains oxyethylene units, the amountof oxyethylene units is preferably 20% by weight or more, morepreferably 30% by weight or more, still more preferably 40% by weight ormore. Furthermore, examples also include polyoxypropylene glycol,polyoxytetramethylene glycol (hereinbelow, abbreviated as “PTMG”), andpolyoxypropylene oxytetramethylene block copolymer diol. Preferred amongthem are PEG, polyoxyethylene oxypropylene block copolymer diol, andpolyoxyethylene oxytetramethylene block copolymer diol, with PEG beingparticularly preferred. Furthermore, polyether diol may be used eithersingly or a mixture of two or more thereof may be used.

Examples of polycarbonate diols include polyhexamethylene carbonatediol. Examples of polyester diols include a condensed polyester diolobtained by reaction of at least one of a low molecular weight diol or apolyether diol having a number average molecular weight of 1,000 or lesswith at least one of the dicarboxylic acids mentioned above; and apolylactone diol obtained by ring-opening polymerization of a lactonehaving a carbon number of 4 to 12. Examples of the low molecular weightdiol include the low molecular weight glycols mentioned above asexamples of the polyether diol. Examples of the polyether diol having anumber average molecular weight of 1,000 or less includepolyoxypropylene glycol and PTMG. Examples of the lactone includeε-caprolactone and γ-valerolactone. Specific examples of the polyesterdiol include polyethylene adipate diol, polybutylene adipate diol,polyneopentylene adipate diol, poly(3-methyl-1,5-pentylene adipate)diol, polyhexamethylene adipate diol, polycaprolactone diol, andmixtures of two or more thereof.

The active hydrogen component may also be a mixture of two or moreselected from the polyether diols, polycarbonate diols, and polyesterdiols.

Preferably, the active hydrogen component essentially contains a highmolecular weight diol having a number average molecular weight of 2,500to 15,000. Examples of the high molecular weight diol include thepolyether diols, polycarbonate diols, and polyester diols.

The high molecular weight diol having a number average molecular weightof 2,500 to 15,000 is preferred for imparting adequate flexibility tothe urethane resin and high strength to a coating formed on the activematerial. Furthermore, the number average molecular weight of the highmolecular weight diol is more preferably 3,000 to 12,500, still morepreferably 4,000 to 10,000. The number average molecular weight of thehigh molecular weight diol) can be calculated from the hydroxyl value ofthe high molecular weight diol, and the hydroxyl value can be measuredin accordance with JIS K1557-1.

Furthermore, it is preferable that the active hydrogen componentessentially contains the high molecular weight diol having a numberaverage molecular weight of 2,500 to 15,000, and the solubilityparameter (hereinbelow, abbreviated as SP value) of the high molecularweight diol is 8.0 to 12.0 (cal/cm³)^(1/2). The SP value of the highmolecular weight diol is more preferably 8.5 to 11.5 (cal/cm³)^(1/2),still more preferably 9.0 to 11.0 (cal/cm³)^(1/2).

The SP value is calculated by the Fedors method. The SP value can beexpressed by the following equation:SP value (δ)=(ΔH/V)^(1/2)

In the formula, ΔH represents the molar evaporation heat (cal), and Vrepresents the molar volume (cm³).

In addition, the total molar evaporation heat (ΔH) and the total molarvolume (V) of the atomic groups described in “POLYMER ENGINEERING ANDSCIENCE, 1974, Vol. 14, No. 2, ROBERT F. FEDORS. (pp. 151-153)” can beused for ΔH and V, respectively.

Those having similar SP values are easily mixed together (highlymiscible), and those having very different SP values are not easilymixed together. Namely, the SP value is an index of miscibility.

SP value of 8.0 to 12.0 (cal/cm³)^(1/2) of polymer diol is preferablefrom the viewpoint of liquid absorption of an electrolyte solution by aurethane resin.

It is also preferable that the active hydrogen component essentiallycontains the high molecular weight diol having a number averagemolecular weight of 2,500 to 15,000, and the content of the polymer diolis 20 to 80% by weight based on the weight of the urethane resin. Thecontent of the polymer dial is more preferably 30 to 70% by weight, andeven more preferably 40 to 65% by weight.

Polymer diol content of 20 to 80% by weight is preferable from theviewpoint of liquid absorption of an electrolyte solution by a urethaneresin.

It is also preferable that the active hydrogen component essentiallycontains a polymer diol having a number average molecular weight of2,500 to 15,000 and a chain extending agent.

Examples of the chain extending agent include low molecular weight diolshaving a carbon number of 2 to 10 (e.g., ethylene glycol (hereinbelow,abbreviated as EG), propylene glycol, 1,4-butane diol (hereinbelow,abbreviated as 14BG), diethylene glycol (hereinbelow, abbreviated asDEG), and 1,6-hexamethylene glycol); diamines [aliphatic diamine havinga carbon number of 2 to 6 (e.g., ethylenediamine and1,2-propylenediamine), alicyclic diamine having a carbon number of 6 to15 (e.g., isophorone diamine and 4,4′-diaminodicyclohexylmethane),aromatic diamines having a carbon number of 6 to 15 (e.g.,4,4′-diaminodiphenylmethane)]; monoalkanolamines (e.g.,monoethanolamine); hydrazine or its derivatives (e.g., adipic aciddihydrazide); and mixtures of two or more thereof. Preferred among themare low molecular weight diols, with EG, DEG, and 14BG beingparticularly preferred.

A preferred combination of the high molecular weight diol and the chainextending agent is a combination of PEG as the high molecular weightdiol and EG as the chain extending agent or a combination of apolycarbonate diol as the high molecular weight diol and EG as the chainextending agent.

Preferably, the active hydrogen component contains the high molecularweight diol (a11) having a number average molecular weight of 2,500 to15,000, a diol (a12) other than the high molecular weight, and the chainextending agent (a13) and the equivalent ratio of (a11) to (a12){(a11)/(a12)} is 10/1 to 30/1 and the equivalent ratio of (a11) to thetotal of (a12) and (a13) {(a11)/[(a12)+(a13)]} is 0.9/1 to 1.1/1.

The equivalent ratio of (a11) to (a12) {(a11)/(a12)} is more preferably13/1 to 25/1, still more preferably 15/1 to 20/1.

The diol other than the high molecular weight diol is not particularlylimited as long as it is a diol and it is not included theaforementioned high molecular weight diol and specific examples thereofinclude a diol having a number average molecular weight of less than2,500, and a diol having a number average molecular weight of more than15,000.

Examples of such diol include the polyether diols, polycarbonate diols,and polyester diols that are mentioned above.

Furthermore, a low molecular weight diol which is a diol other than thehigh molecular weight diol and has a carbon number of 2 to 10 includedin the chain extending agent is not included in the diol other than thehigh molecular weight diol.

Isocyanate conventionally used in the production of polyurethane can beused as the isocyanate component. Examples of such isocyanates includearomatic diisocyanates having a carbon number of 6 to 20 (excludingcarbon atoms in NCO groups; the same shall apply hereinbelow), aliphaticdiisocyanates having a carbon number of 2 to 18, alicyclic diisocyanateshaving a carbon number of 4 to 15, araliphatic diisocyanates having acarbon number of 8 to 15, modified forms of these diisocyanates (such ascarbodiimide-modified diisocyanate, urethane-modified diisocyanate, anduretdione-modified diisocyanate), and mixtures of two or more thereof.

Specific examples of the aromatic diisocyanates include 1,3- and/or1,4-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 2,4′- or4,4′-diphenylmethane diisocyanate (hereinbelow, diphenylmethanediisocyanate is abbreviated as “MDI”), 4,4′-diisocyanato biphenyl,3,3′-dimethyl-4,4′-diisocyanato biphenyl,3,3′-dimethyl-4,4′-diisocyanato diphenylmethane, and 1,5-naphthylenediisocyanate.

Specific examples of the aliphatic diisocyanates include ethylenediisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate,dodecamethylene diisocyanate, 2,2,4-trimethyl hexamethylenediisocyanate, lysine diisocyanate, 2,6-diisocyanato methylcaproate,bis(2-isocyanatoethyl)carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexanoate.

Specific examples of the alicyclic diisocyanate include isophoronediisocyanate, dicyclohexylmethane-4,4′-diisocyanate, cyclohexylenediisocyanate, methylcyclohexylene diisocyanate,bis(2-isocyanatoethyl)-4-cyclohexylene-1,2-dicarboxylate, and 2,5-and/or 2,6-norbornane diisocyanate.

Specific examples of the araliphatic diisocyanate include m- and/orp-xylylene diisocyanate and α,α,α′,α′-tetramethylxylylene diisocyanate.

Preferred among them are aromatic diisocyanates and alicyclicdiisocyanates, more preferred are aromatic diisocyanates, and still moreparticularly preferred is MDI.

In a case in which the urethane resin contains the high molecular weightdiol (a11) and the isocyanate component (a2), a preferred equivalentratio of (a2)/(a11) is 10 to 30/1, and more preferably 11 to 28/1. Ifthe ratio of the isocyanate component is more than 30 equivalents, theresulting coating will be stiff.

In a case in which the urethane resin contains the high molecular weightdiol (a11), the chain extending agent (a13), and the isocyanatecomponent (a2), the equivalent ratio of (a2)/[(a11)+(a13)] is usually0.9 to 1.1/1, preferably 0.95 to 1.05/1. If the equivalent ratio isoutside the above range, the molecular weight of the urethane resin maynot be sufficiently high.

The number average molecular weight of the urethane resin is preferably40,000 to 500,000, and more preferably 50,000 to 400,000. If the numberaverage molecular weight of the urethane resin is less than 40,000, theresulting coating will have low strength, whereas if the number averagemolecular weight thereof is more than 500,000, the solution of theurethane resin will have high viscosity, and a uniform coating may notbe obtained.

The number average molecular weight of the urethane resin is measured bygel permeation chromatography (hereinbelow, abbreviated as GPC) usingDMF as a solvent and polyoxypropylene glycol as a standard substance.The sample concentration may be 0.25% by weight; the column solid phasemay be one in which each of the following columns is connected together:TSKgel SuperH2000, TSKgel SuperH3000, and TSKgel SuperH4000 (allavailable from Tosoh Corporation); and the column temperature may be 40°C.

The urethane resin can be produced by reaction of an active hydrogencomponent with an isocyanate component.

Examples of methods for producing the urethane resin include a one shotmethod in which the high molecular weight diol and the chain extendingagent are used as the active hydrogen components, and the isocyanatecomponent is simultaneously reacted with the high molecular weight dioland the chain extending agent, and a prepolymer method in which the highmolecular weight diol and the isocyanate component are reacted first,and the chain extending agent is subsequently reacted.

In addition, the urethane resin can be produced in the presence orabsence of a solvent inactive to an isocyanate group. Examples ofsuitable solvents to be used in the reaction in the presence of asolvent include amide-based solvents [e.g., dimethyl formamide(hereinbelow, abbreviated as DMF), dimethyl acetamide], sulfoxide-basedsolvents (e.g., dimethyl sulfoxide), ketone-based solvents (e.g., methylethyl ketone and methyl isobutyl ketone), aromatic solvents (e.g.,toluene and xylene), ether-based solvents (e.g., dioxane andtetrahydrofuran), ester-based solvents (e.g., ethyl acetate and butylacetate), and mixtures of two or more thereof. Preferred among these areamide-based solvents, ketone-based solvents, aromatic solvents, andmixtures of two or more thereof.

In the production of the urethane resin, the reaction temperature may bea temperature commonly used in a urethanation reaction, and it isusually 20° C. to 100° C. in the presence of a solvent, and is usually20° C. to 220° C. in the absence of a solvent.

To facilitate the reaction, a catalyst commonly used in a polyurethanereaction [e.g., an amine-based catalyst (such as triethylamine ortriethylene diamine) or a tin-based catalyst (such as dibutyl tindilaurate)] may be used as needed.

In addition, a polymerization terminator [e.g., a monohydric alcohol(such as ethanol, isopropanol, or butanol) or a monovalent amine (suchas dimethylamine or dibutylamine) may also be used as needed.

The urethane resin can be produced using a production apparatus commonlyused in the relevant industry. In the absence of a solvent, a productionapparatus such as a kneader or extruder can be used. The solutionviscosity of the thus-produced urethane resin as measured in a 30% byweight (solids) solution in DMF is usually 10 to 10,000 poise/20° C.,and from a practical standpoint, it is preferably 100 to 2,000 poise/20°C.

Furthermore, according to a preferred embodiment of the presentinvention, a polymer having a vinyl monomer as an essentialconstitutional monomer is also preferred as a coating resin. The polymerhaving a vinyl monomer as an essential constitutional monomer hasflexibility, and thus it is possible to alleviate the volume change ofthe electrode and suppress expansion of the electrode according tocoating the active material with the polymer.

The coating resin is preferably obtained by including a polymer whichhas a liquid absorption rate of 10% or more when immersed in anelectrolyte solution and a tensile elongation at break of 10% or more ina saturated liquid absorption state, and has a vinyl monomer as anessential constitutional monomer.

In particular, it is preferable to include, as a vinyl monomer, a vinylmonomer having a carboxy group and a vinyl monomer represented by thefollowing general formula (1)CH₂═C(R¹)COOR²  (1)

In the formula (1), R¹ is a hydrogen atom or a methyl group; and R² is alinear alkyl group having a carbon number of 1 to 4 or a branched alkylgroup having a carbon number of 4 to 36.

Examples of the vinyl monomer having a carboxyl group includemonocarboxylic acids having a carbon number of 3 to 15 such as(meth)acrylic acid, crotonic acid, and cinnamic acid; dicarboxylic acidshaving a carbon number of 4 to 24 such as maleic acid (anhydride),fumaric acid, itaconic acid (anhydride), citraconic acid, and mesaconicacid; and trivalent, tetravalent, or higher polycarboxylic acids havinga carbon number of 6 to 24 such as aconitic acid. Preferred among theseis (meth)acrylic acid, with methacrylic acid being particularlypreferred.

In the vinyl monomer represented by the above general formula (1), R¹ isa hydrogen atom or a methyl group. R¹ is preferably a methyl group.

R² is a linear alkyl group having a carbon number of 1 to 4 or abranched alkyl group having a carbon number of 4 to 36. Specificexamples of R² include a methyl group, an ethyl group, a propyl group, a1-alkyl alkyl group (1-methylpropyl group (sec-butyl group),1,1-dimethylethyl group (tert-butyl group), 1-methylbutyl group, a1-ethylpropyl group, a 1,1-dimethyl propyl group, a 1-methylpentylgroup, a 1-ethylbutyl group, a 1-methylhexyl group, a 1-ethyl pentylgroup, a 1-methyl heptyl group, a 1-ethylhexyl group, a 1-methyl octylgroup, a 1-ethyl heptyl group, a 1-methyl nonyl group, a 1-ethyl octylgroup, a 1-methyldecyl group, a 1-ethyl nonyl group, a 1-butyl eicosylgroup, a 1-hexyl octadecyl group, a 1-octyl hexadecyl group, a 1-decyltetradecyl group, a 1-undecyl tridecyl group or the like), 2-alkyl alkylgroup (2-methylpropyl group (iso-butyl group), 2-methylbutyl group, a2-ethylpropyl group, a 2,2-dimethyl propyl group, a 2-methylpentylgroup, a 2-ethylbutyl group, a 2-methylhexyl group, a 2-ethyl pentylgroup, a 2-methyl heptyl group, a 2-ethylhexyl group, a 2-methyl octylgroup, a 2-ethyl heptyl group, a 2-methyl nonyl group, a 2-ethyl octylgroup, a 2-methyldecyl group, a 2-ethyl nonyl group, a 2-hexyl octadecylgroup, a 2-octyl hexadecyl group, a 2-decyl tetradecyl group, a2-undecyl tridecyl group, a 2-dodecyl hexadecyl group, a 2-tridecylpentadecyl group, a 2-decyl octadecyl group, a 2-tetradecyl octadecylgroup, a 2-hexadecyl octadecyl group, a 2-tetradecyl eicosyl group, a2-hexadecyl eicosyl group or the like), 3 to 34-alkylalkyl groups (suchas 3-alkyl alkyl group, 4-alkyl alkyl group, 5-alkyl alkyl group,32-alkyl alkyl group, 33-alkyl alkyl group, and 34-alkyl alkyl group);mixed alkyl groups containing one or more branched alkyl groups such asresidues of oxo alcohols produced corresponding to propylene oligomers(from heptamer to undecamer), ethylene/propylene (molar ratio of 16/1 to1/11) oligomers, isobutylene oligomers (from heptamer to octamer), andα-olefin (having a carbon number of 5 to 20) oligomer (from tetramer tooctamer).

Preferred among these are a methyl group, an ethyl group, and a 2-alkylalkyl group from the viewpoint of liquid absorption of an electrolytesolution, with a 2-ethylhexyl group and a 2-decyltetradecyl group beingmore preferred.

In addition to a vinyl monomer and the vinyl monomer represented by theabove general formula (1), the monomers constituting the polymer mayalso include (contain) a copolymerizable vinyl monomer (b3) free ofactive hydrogen.

Examples of the copolymerizable vinyl monomer (b3) free of activehydrogen include the following monomers (b31) to (b35).

(b31) Hydrocarbyl (meth)acrylates Formed from Monool Having CarbonNumber of 1 to 20 and (meth)acrylic Acid

Examples of the monool include (i) aliphatic monools [such as methanol,ethanol, n- or i-propyl alcohol, n-butyl alcohol, n-pentyl alcohol,n-octyl alcohol, nonyl alcohol, decyl alcohol, lauryl alcohol, tridecylalcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol]; (ii)alicyclic monools [such as cyclohexyl alcohol]; (iii) araliphaticmonools [such as benzyl alcohol]; and mixtures of two or more thereof.

(b32) Poly (n=2 to 30)oxyalkylene (having a carbon number of 2 to 4)alkyl (having a carbon number of 1 to 18) ether (meth)acrylates [such as(meth)acrylate of ethylene oxide (hereinbelow, abbreviated as “EO”) (10mol) adduct of methanol, and (meth)acrylate of propylene oxide(hereinbelow, abbreviated as “PO”) (10 mol) adduct of methanol]

(b33) Nitrogen-Containing Vinyl Compounds

(b33-1) Amide Group-Containing Vinyl Compounds

(i) (Meth)acrylamide compounds having a carbon number of 3 to 30, e.g.,N,N-dialkyl (having a carbon number of 1 to 6) or diaralkyl (having acarbon number of 7 to 15) (meth)acrylamides [such asN,N-dimethylacrylamide and N,N-dibenzylacrylamide], and diacetoneacrylamide

(ii) Amide group-containing vinyl compounds having a carbon number of 4to 20 excluding the above (meth)acrylamide compounds, e.g.,N-methyl-N-vinylacetamide and cyclic amides (such as pyrrolidonecompounds (having a carbon number of 6 to 13, e.g., N-vinylpyrrolidone)).

(b33-2) (Meth)acrylate Compounds

(i) Dialkyl (having a carbon number of 1 to 4) aminoalkyl (having acarbon number of 1 to 4) (meth)acrylates [such as N,N-dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, t-butylaminoethyl(meth)acrylate, and morpholinoethyl (meth)acrylate]

(ii) Quaternary ammonium group-containing (meth)acrylates [quaternarycompounds obtained by quaternizing tertiary amino group-containing(meth)acrylates [such as N,N-dimethylaminoethyl (meth)acrylate andN,N-diethylaminoethyl (meth)acrylate] with a quaternizing agent (such asquaternary product obtained by using the quaternizing agent)]

(b33-3) Heterocyclic Ring-Containing Vinyl Compounds

Pyridine compounds (having a carbon number of 7 to 14, e.g., 2- or4-vinyl pyridine), imidazole compounds (having a carbon number of 5 to12, e.g., N-vinyl imidazole), pyrrole compounds (having a carbon numberof 6 to 13, e.g., N-vinyl pyrrole), and pyrrolidone compounds (having acarbon number of 6 to 13, e.g., N-vinyl-2-pyrrolidone)

(b33-4) Nitrile Group-Containing Vinyl Compounds

Nitrile group-containing vinyl compounds having a carbon number of 3 to15, e.g., (meth)acrylonitrile, cyanostyrene, and cyanoalkyl (having acarbon number of 1 to 4) acrylate

(b33-5) Other Nitrogen-Containing Vinyl Compounds

Nitro group-containing vinyl compounds (having a carbon number of 8 to16, e.g., nitrostyrene)

(b34) Vinyl Hydrocarbons

(b34-1) Aliphatic Vinyl Hydrocarbons

Olefins having a carbon number of 2 to 18 or more [such as ethylene,propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene,dodecene, and octadecene], dienes having a carbon number of 4 to 10 ormore [such as butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, and1,7-octadiene)

(b34-2) Alicyclic Vinyl Hydrocarbons

Cyclic unsaturated compounds having a carbon number of 4 to 18 or more,e.g., cycloalkene (e.g., cyclohexene), (di)cycloalkadiene [e.g.,(di)cyclopentadiene], terpene (e.g., pinene, limonene, and indene)

(b34-3) Aromatic Vinyl Hydrocarbons

Aromatic unsaturated compounds having a carbon number of 8 to 20 ormore, e.g., styrene, α-methyl styrene, vinyl toluene, 2,4-dimethylstyrene, ethyl styrene, isopropyl styrene, butyl styrene, phenylstyrene, cyclohexyl styrene, and benzyl styrene

(b35) Vinyl Esters, Vineyl Ethers, Vinyl Ketones, UnsaturatedDicarboxylic Acid Diesters

(b35-1) Vinyl Esters

Aliphatic vinyl esters [having a carbon number of 4 to 15, e.g., alkenylesters of aliphatic carboxylic acid (mono- or dicarboxylic acid) (e.g.,vinyl acetate, vinyl propionate, vinyl butyrate, diallyl adipate,isopropenyl acetate, and vinyl methoxy acetate)], aromatic vinyl esters[having a carbon number of 9 to 20, e.g., alkenyl esters of aromaticcarboxylic acid (mono- or dicarboxylic acid) (e.g., vinyl benzoate,diallyl phthalate, methyl-4-vinyl benzoate), and aromaticring-containing esters of aliphatic carboxylic acid (e.g.,acetoxystyrene)]

(b35-2) Vinyl Ethers

Aliphatic vinyl ethers [having a carbon number of 3 to 15, e.g., vinylalkyl (having a carbon number of 1 to 10) ether (such as vinyl methylether, vinyl butyl ether, and vinyl 2-ethylhexyl ether), vinyl alkoxy(having a carbon number of 1 to 6) alkyl (having a carbon number of 1 to4) ethers (such as vinyl-2-methoxyethyl ether, methoxybutadiene,3,4-dihydro-1,2-pyran, 2-butoxy-2′-vinyloxy diethyl ether, andvinyl-2-ethylmercapto ethyl ether), and poly(2 to 4) (meth)allyloxyalkane (having a carbon number of 2 to 6) (such asdiallyloxyethane, triallyloxyethane, tetraallyloxybutane, andtetramethallyloxyethane)], aromatic vinyl ethers (having a carbon numberof 8 to 20, e.g., vinyl phenyl ether and phenoxystyrene)

(b35-3) Vinyl Ketones

Aliphatic vinyl ketones (having a carbon number of 4 to 25, e.g., vinylmethyl ketone and vinyl ethyl ketone), aromatic vinyl ketones (having acarbon number of 9 to 21, e.g., vinyl phenyl ketone)

(b35-4) Unsaturated Dicarboxylic Acid Diesters

Unsaturated dicarboxylic acid diesters having a carbon number of 4 to34, e.g., dialkyl fumarate (two alkyl groups are each a linear,branched, or alicyclic group having a carbon number of 1 to 22) anddialkyl maleate (two alkyl groups are each a linear, branched, oralicyclic group having a carbon number of 1 to 22)

Preferred among the above examples of the monomer (b3) in terms ofliquid absorption of electrolyte solution and withstand voltage are themonomers (b31), (b32), and (b33), with methyl (meth)acrylate, ethyl(meth)acrylate, and butyl (meth)acrylate among the monomers (b31) beingmore preferred.

In the polymer, content of the vinyl monomer (b1) having a carboxylgroup, the vinyl monomer (b2) represented by the above formula (1), thecopolymerizable vinyl monomer (b3) free of active hydrogen is preferablyas follows based on the weight of the polymer: (b1) is 0.1 to 80% byweight, (b2) is 0.1 to 99.9% by weight, and (b3) is 0 to 99.8% byweight.

As the content of these monomers are in the above ranges, a favorableliquid absorption property for an electrolyte solution is obtained.

More preferred content is 30 to 60% by weight for (b1), 5 to 60% byweight for (b2), and 5 to 80% by weight for (b3); and still morepreferred amounts are 35 to 50% by weight for (b1), 15 to 45% by weightfor (b2), and 20 to 60% by weight for (b3).

The lower limit of the number average molecular weight of the polymer ispreferably 3,000, more preferably 50,000, particularly preferably100,000, and most preferably 200,000. The upper limit thereof ispreferably 2,000,000, more preferably 1,500,000, particularly preferably1,000,000, and most preferably 800,000.

The number average molecular weight of the polymer can be measured byGPC (gel permeation chromatography) under the following conditions.

Device: Alliance GPC V2000 (manufactured by Waters.)

Solvent: ortho-dichlorobenzene

Standard substance: polystyrene

Sample concentration: 3 mg/ml

Column solid phase: two PL gel 10 μm MIXED-B columns connected in series(manufactured by Polymer Laboratories Limited)

Column temperature: 135° C.

The solubility parameter (“SP value”) of the polymer is preferably 9.0to 20.0 (cal/cm³)^(1/2). The SP value of the polymer is more preferably10.0 to 18.0 (cal/cm³)^(1/2), still more preferably 11.5 to 14.0(cal/cm³)^(1/2). The polymer having an SP value of 9.0 to 20.0(cal/cm³)^(1/2) is preferred in terms of liquid absorption of theelectrolyte solution.

The glass transition point [hereinbelow, abbreviated as “Tg”;measurement method: differential scanning calorimetry (DSC)] of thepolymer is preferably 80° C. to 200° C., more preferably 90° C. to 180°C., and particularly preferably 100° C. to 150° C., from the viewpointof heat resistance of the battery.

The polymer can be produced by a known polymerization method (such asbulk polymerization, solution polymerization, emulsion polymerization,or suspension polymerization).

Polymerization can be carried out using a known polymerization initiator[e.g., an azo-based initiator [such as2,2′-azobis(2-methylpropionitrile) or2,2′-azobis(2,4-dimethylvaleronitrile)], or a peroxide-based initiator(such as benzoyl peroxide, di-t-butylperoxide, or lauryl peroxide)].

The amount of the polymerization initiator to be used based on the totalmonomer weight is preferably 0.01 to 5% by weight, and more preferably0.03 to 2% by weight.

In the case of solution polymerization, examples of solvents to be usedinclude esters (having a carbon number of 2 to 8, e.g., ethyl acetateand butyl acetate), alcohols (having a carbon number of 1 to 8, e.g.,methanol, ethanol, and octanol), hydrocarbons (having a carbon number of4 to 8, e.g., n-butane, cyclohexane, and toluene), and ketones (having acarbon number of 3 to 9, e.g., methyl ethyl ketone), and they may beused as a mixture of two or more types. The amount to be used based onthe total monomer weight is usually 5 to 900%, and preferably 10 to400%. The monomer concentration is usually 10 to 95% by weight, andpreferably 20 to 90% by weight.

In the case of emulsion polymerization and suspension polymerization,examples of dispersion mediums to be used include water, alcohols (e.g.,ethanol), esters (e.g., ethyl propionate), and light naphtha; andexamples of emulsifiers to be used include metal salts of higher fattyacids (having a carbon number of 10 to 24) (e.g., sodium oleate andsodium stearate), metal salts of sulfates of higher alcohol (having acarbon number of 10 to 24) (e.g., sodium lauryl sulfate), ethoxylatedtetramethyl decyne diol, sodium sulfoethyl methacrylate, anddimethylamino methyl methacrylate. Further, a stabilizer such aspolyvinyl alcohol or polyvinyl pyrrolidone may be added.

The monomer concentration in the solution or the dispersion is usually 5to 95% by weight. The amount of the polymerization initiator to be usedbased on the total monomer weight is usually 0.01 to 5% by weight, andpreferably 0.05 to 2% by weight from the viewpoint of the adhesive forceand aggregational force.

Polymerization can be carried out using a known chain transfer agent.For example, a mercapto compound (such as dodecyl mercaptan or n-butylmercaptan) or a halogenated hydrocarbon (such as carbon tetrachloride,carbon tetrabromide, or benzyl chloride) can be used. The amount to beused based on the total monomer weight is usually 2% by weight or less,and preferably 0.5% by weight or less from the viewpoint of the adhesiveforce and aggregational force.

In addition, the system temperature in the polymerization reaction isusually −5° C. to 150° C., and preferably 30° C. to 120° C. The reactiontime is usually 0.1 to 50 hours, and preferably 2 to 24 hours. Thetermination of the reaction can be confirmed by the amount of unreactedmonomers which is usually 5% by weight or less, and preferably 1% byweight or less of the total amount of the monomers used.

The coating resin may be a crosslinked polymer which is obtained bycrosslinking the polymer with a polyepoxy compound and/or a polyolcompound.

As for the crosslinked polymer, it is preferred to crosslink the polymerusing a crosslinking agent having a reactive functional group thatreacts with active hydrogen of a carboxyl group or the like in thepolymer, and it is preferred to use the polyepoxy compound and/or thepolyol compound as the crosslinking agent.

The polyepoxy compound has an epoxy equivalent of 80 to 2,500. Examplesthereof include glycidyl ethers [such as bisphenol A diglycidyl ether,bisphenol F diglycidyl ether, pyrogallol triglycidyl ether, ethyleneglycol diglycidyl ether, propylene glycol diglycidyl ether, neopentylglycol diglycidyl ether, trimethylol propane triglycidyl ether, glycerintriglycidyl ether, polyethylene glycol (Mw 200 to 2,000) diglycidylether, polypropylene glycol (Mw 200 to 2,000) diglycidyl ether, anddiglycidyl ether of bisphenol A alkylene oxide (1 to 20 mol) adduct];glycidyl esters (such as phthalic acid diglycidyl ester, trimelliticacid triglycidyl ester, dimer acid diglycidyl ester, and adipic aciddiglycidyl ester); glycidylamines [such as N,N-diglycidylaniline,N,N-diglycidyltoluidine, N,N,N′,N′-tetraglycidyldiaminodiphenylmethane,N,N,N′,N′-tetraglycidylxylylenediamine,1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, andN,N,N′,N′-tetraglycidylhexamethylenediamine]; aliphatic epoxides (suchas epoxidized polybutadiene and epoxidized soybean oil); and alicyclicepoxides (such as limonene dioxide and dicyclopentadiene dioxide).

Examples of the polyol compound include low molecular weight polyhydricalcohols [aliphatic or alicyclic diols having a carbon number of 2 to 20[such as EG, DEG, propylene glycol, 1,3-butylene glycol, 1,4BG,1,6-hexane diol, 3-methylpentane diol, neopentyl glycol, 1,9-nonanediol, 1,4-dihydroxycyclohexane, 1,4-bis(hydroxymethyl)cyclohexane, and2,2-bis(4,4′-hydroxycyclohexyl)propane]; aromatic ring-containing diolshaving a carbon number of 8 to 15 [such as m- or p-xylylene glycol and1,4-bis(hydroxyethyl)benzene]; triols having a carbon number of 3 to 8(such as glycerin and trimethylol propane); tetrahydric or higherpolyhydric alcohols [such as pentaerythritol, α-methylglucoside,sorbitol, xylite, mannitol, glucose, fructose, sucrose,dipentaerythritol, and polyglycerin (polymerization degree of 2 to20)]], and alkylene (having a carbon number of 2 to 4) oxide adducts(polymerization degree of 2 to 30) thereof.

As for the amount of the crosslinking agent to be used, the equivalentratio of active hydrogen-containing groups in the polymer to reactivefunctional groups in the crosslinking agent is preferably 1:0.01 to 2,more preferably 1:0.02 to 1, in terms of liquid absorption of theelectrolyte solution.

Examples of methods for crosslinking the polymer using the crosslinkingagent include a method in which an active material is coated with acoating resin consisting of the polymer followed by crosslinking.Specifically, an active material and a resin solution containing thepolymer are mixed together and a solvent is removed from the mixture soas to produce a coated active material in which the active material iscoated with the resin. Then, a solution containing the crosslinkingagent is mixed with the coated active material, and the mixture isheated to remove the solvent and subjected to a crosslinking reaction.In this manner, the active material is coated with the crosslinkedpolymer.

The heating temperature is preferably 70° C. or higher in the case ofusing the polyepoxy compound as a crosslinking agent, and is preferably120° C. or higher in the case of using the polyol compound as acrosslinking agent.

(Method for Producing Coated Active Material)

The coated active material coated with a coating agent can be obtainedas follows, for example; an active material is added to a universalmixer and stirred at 10 to 500 rpm, and in the same state, a resinsolution containing a coating resin (i.e., resin solution for coating)is added dropwise and mixed over 1 to 90 minutes followed by mixing witha conduction assisting agent, the temperature is increased to 50 to 200°C. under stirring, and the pressure is lowered to 0.007 to 0.04 MPafollowed by maintaining it for 10 to 150 minutes. Furthermore, as asolvent for the resin solution, alcohols such as methanol, ethanol, orisopropanol can be suitably used.

The blending ratio between the resin for coating an active material andconduction assisting agent is, although not particularly limited,preferably as follows; resin for coating an active material (resin solidweight):conduction assisting agent=1:0.2 to 3.0 in terms of weightratio.

The blending ratio between the active material and resin for coating anactive material (resin solid weight) is, although not particularlylimited, preferably as follows; active material:resin for coating anactive material (resin solid weight)=1:0.001 to 0.1 in terms of weightratio.

Furthermore, although the resin solution for coating contains a coatingresin and solvent, it may be prepared by mixing a coating resin and aconduction assisting agent depending on a case. By further mixing aresin solution for coating, which has been mixed in advance, with anactive material, the active material can be coated with a resin solutionfor coating (i.e., coating agent).

Furthermore, it is also possible that, when the active material iscoated with a resin solution for coating (i.e., coating agent), thecoating resin, active material, and conduction assisting agent aresimultaneously admixed with one another, and surface of the activematerial is coated with a resin solution for coating (i.e., coatingagent) which contains the coating resin and conduction assisting agent.

Furthermore, it is also possible that, when the active material iscoated with a resin solution for coating (i.e., coating agent), theactive material is admixed with the coating resin followed by mixingwith a conduction assisting agent, and surface of the active material iscoated with a resin solution for coating (i.e., coating agent) whichcontains the coating resin and conduction assisting agent.

As described above, regarding the coated active material, at least apart of the active material is coated with a coating agent that includesa coating resin and a conduction assisting agent. Depending on one'sopinion, such mode can be found to have a core-shell structure.According to this consideration, the average particle diameter of a corepart (active material) is, although not particularly limited, preferably1 to 100 μm, and more preferably 1 to 20 μm from the viewpoint of havinghigher output power. The thickness of the shell part is not particularlylimited, either, but as a thickness of a state in which a gel is notformed, the thickness thereof is preferably 0.01 to 5 μm, and morepreferably 0.1 to 2 μm. In addition, as a thickness after the shell partis immersed in an electrolyte solution (1 M LiPF₆, ethylene carbonate(EC)/diethyl carbonate (DEC)=3/7 (volume ratio)) at 50° C. for 3 days,the thickness thereof is preferably 0.01 to 10 μm, and more preferably0.1 to 5 μm.

(Electrolyte Solution)

According to an embodiment of the present invention, the electrolytesolution contained in two electrodes having different polarity or theelectrolyte layer is a gel phase electrolyte, and the electrolytesolution contained in an active material layer of the two electrodeshaving different polarity can be a gel phase electrolyte. The method forhaving a gel phase electrolyte included in the active material layer isnot particularly limited. According to the mode of FIG. 8, on a secondprincipal surface 62 of a non-woven fabric 60, slurry containing acoated active material may also include a gel phase electrolyte.According to the mode of FIG. 9, slurry containing a conductive member213 and a coated active material may include a gel phase electrolyte.According to the mode of FIG. 10, the composition for active materialcontaining the positive electrode active material 14, conductive fiber213, and resin 214 may include a gel phase electrolyte. Furthermore, thegel phase electrolyte may be included also by impregnating a gel phaseelectrolyte in the active material layer prepared as described above.

Herein, the gel phase electrolyte can be produced by having a step ofincluding a gelling agent in a liquid electrolyte. It is sufficient fora liquid electrolyte to have a state in which supporting salts aredissolved in an organic solvent. Examples of the organic solvent whichmay be used include lactone compounds, cyclic or chain-like carbonateesters, chain-like carboxylate esters, cyclic or chain-like ethers,phosphate esters, nitrile compounds, amide compounds, sulfone,sulfolane, and mixtures thereof. Examples thereof include carbonatessuch as ethylene carbonate (EC), propylene carbonate (PC), dimethylcarbonate (DMC), diethyl carbonate (DEC), or ethyl methyl carbonate.Preferred among the organic solvents, in terms of output power of thebattery and charge-discharge cycle characteristics, are lactonecompounds, cyclic carbonate esters, chain-like carbonate esters, andphosphate esters. Lactone compounds, cyclic carbonate esters, andchain-like carbonate esters are more preferred, and mixtures of cycliccarbonate esters and chain-like carbonate esters are particularlypreferred. Mixtures of ethylene carbonate (EC) and diethyl carbonate(DEC) are most preferred.

The gel phase electrolyte obtained by including a gelling agent in aliquid electrolyte preferably has conductivity of 0.1 mS/cm or higher.More preferably, the conductivity is 0.1 to 2 mS/cm, and it can be 0.5to 2 mS/cm.

As the strength of a gel phase material increases, a conductivity of thegel phase material is lowered, and as the gel phase material becomescloser to a liquid phase, the conductivity is increased. Thus, theconductivity of a gel phase material can be used as an indexrepresenting the strength of a gel phase material. To form a thickelectrode, which is the object of the present invention, strength of anelectrode needs to be increased in a related art. As such, if theconductivity of a gel phase electrolyte is within a desirable range, itis desirable both the electric performances of a battery and strength ofan electrode can be obtained simultaneously.

Furthermore, the conductivity of a gel phase electrolyte which is usedfor the non-aqueous electrolyte secondary battery of the presentinvention can be measured by the following method, and by addingpreferable parts of a gelling agent or the like described below to aliquid electrolyte, the conductivity can be adjusted to a suitablerange.

[Method for Measuring Conductivity]

By gelling a mixture in which a liquid electrolyte and a gelling agentare admixed with each other at the same ratio as it is used for thenon-aqueous electrolyte secondary battery of the present invention, agel electrolyte is prepared. By using the prepared gel electrolyte, theconductivity is measured at 25° C. by an AC impedance method in view ofthe method of measuring conduction rate of fine ceramic ion conductor ofJIS R 1661-2004.

As a gelling agent, a monomer for gellation can be used, for example.Examples of the monomer for gellation include a monomer or an oligomerwhich has at least two thermal polymerizable polymerization groups inone molecule. Furthermore, according to a preferred embodiment of thepresent invention, the matrix polymer for forming the gel phaseelectrolyte includes carboxylic acid ester as a functional group. When agel matrix polymer of an electrolyte solution is a gel matrix polymerwhich has the same functional group as the functional group of a solventfor constituting an electrolyte solution, carboxylic acid ester isincluded as a functional group.

Examples of the monomer for gellation include bifunctional acrylate suchas ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate,triethylene glycol di(meth)acrylate, tetraethylene glycoldi(meth)acrylate, propylene di(meth)acrylate, dipropylenedi(meth)acrylate, tri propylene di(meth)acrylate, 1,3-butane dioldi(meth)acrylate, 1,4-butane diol di(meth)acrylate, or 1,6-hexane dioldi(meth)acrylate, trifunctional acrylate such as trimethylol propanetri(meth)acrylate or pentaerythritol tri(meth)acrylate, andtetrafunctional acrylate such as ditrimethylol propanetetra(meth)acrylate or pentaerythritol tetra (meth)acrylate, but notlimited thereto. Other than those described above, further examplesinclude a monomer such as urethane acrylate or urethane methacrylate, acopolymer oligomer thereof, and a copolymer oligomer with acrylonitrile,but not limited thereto. Those monomers for gellation are preferablyused in combination of two or more types thereof.

Use amount of the monomer for gellation (in the case of combined use oftwo or more types, total amount thereof) is not particularly limited.However, from the viewpoint of the structural stability of an electrodeand opposing ion conductivity, it is preferably 1 to 30 parts by weight,more preferably 2 to 20 parts by weight, and even more preferably 4 to10 parts by weight relative to 100 parts by weight of a liquidelectrolyte (i.e., organic solvent). If it is 5.0 parts by weight ormore, in particular, the effect of having further enhanced cyclecharacteristics can be obtained.

According to a preferred embodiment, the matrix polymer for forming agel phase electrolyte is obtained by adding a thermal polymerizationinitiator to an electrolyte solution which contains a mixture of atleast a molecule having two polymerizable groups and a molecule havingthree polymerizable groups, and gelling the electrolyte solution bythermal polymerization. It is believed that, according to combined useof a bifunctional group and a trifunctional group, hardness of a gel canbe obtained without lowering the required ion conductivity.

The liquid electrolyte may also contain additives other than thecomponents that are described above. Specific examples of such compoundsinclude vinylene carbonate, methylvinylene carbonate, dimethylvinylenecarbonate, phenylvinylene carbonate, diphenylvinylene carbonate,ethylvinylene carbonate, diethylvinylene carbonate, vinylethylenecarbonate, 1,2-divinylethylene carbonate, 1-methyl-1-vinylethylenecarbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-1-vinylethylenecarbonate, 1-ethyl-2-vinylethylene carbonate, vinylvinylene carbonate,arylethylene carbonate, vinyloxymethylethylene carbonate,aryloxymethylethylene carbonate, acryloxymethylethylene carbonate,methacryloxymethylethylene carbonate, ethynylethylene carbonate,propartylethylene carbonate, ethynyloxymethylethylene carbonate,propartyloxyethylene carbonate, methylene ethylene carbonate, and1,1-dimethyl-2-methylene ethylene carbonate. Among them, vinylenecarbonate, methylvinylene carbonate, and vinylethylene carbonate arepreferable, and vinylene carbonate and vinylethylene carbonate are morepreferable. Those cyclic carbonate esters may be used either singly orin combination of two or more types thereof.

Furthermore, the type of the thermal polymerization imitator is notparticularly limited. However, an initiator which can react at atemperature at which an electrolyte solution does not decompose and ofwhich decomposition product is not easily oxidized or reduced ispreferable. Examples thereof which can be used include t-butylperoxypyvalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate,t-hexylperoxy pyvalate, t-butylperoxy-2-ethyl hexanoate, andt-butylperoxy isobutyrate. The time for thermal polymerization is notparticularly limited, either, but it is 10 to 300 minutes or so.

[Other Components]

At least one of the active material layers contain a conductive memberformed of an electron conducting material and a coated active material.Other than those, the electrolyte solution may also contain an ionconductive polymer, supporting salts, or the like.

(Ion Conductive Polymer)

Examples of the ion conductive polymer include a polymer of polyethyleneoxide (PEO) and polypropylene oxide (PPO).

(Supporting Salts)

Examples of the supporting salts include lithium salts of inorganicacids such as LiPF₆, LiBF₄, LiSbF₆, LiAsF₆, and LiClO₄; and lithiumsalts of organic acids such as LiN(CF₃SO₂)₂, LiN(C₂F₅SO₂)₂, andLiC(CF₃SO₂)₃. LiPF₆ is preferred among them in terms of output power ofthe battery and charge-discharge cycle characteristics.

The blending ratio of the components that are included in an activematerial layer is not particularly limited. The blending ratio can beadjusted according to suitable reference to the knowledge known for alithium ion secondary battery. The thickness of each active materiallayer is not particularly limited, either, and reference can be madesuitably to the knowledge known for a battery.

[Electrolyte Layer]

The electrolyte used for the electrolyte layer 17 of this embodiment canbe a gel phase electrolyte. Because the gel phase electrolyte has beenalready explained above, further explanations are omitted herein.

In the bipolar secondary battery of this embodiment, a separator may beused in an electrolyte layer. The separator has a function of holding anelectrolyte so as to secure the lithium ion conductivity between apositive electrode and a negative electrode and a function of serving asa partition wall between a positive electrode and a negative electrode.

Examples of a separator form include a porous sheet separator or anon-woven separator composed of a polymer or a fiber which absorbs andmaintains the electrolyte.

As a porous sheet separator composed of a polymer or a fiber, amicroporous (microporous membrane) separator can be used, for example.Specific examples of the porous sheet composed of a polymer or a fiberinclude a microporous (microporous membrane) separator which is composedof polyolefin such as polyethylene (PE) and polypropylene (PP); alaminate in which a plurality of them are laminated (for example, alaminate with three-layer structure of PP/PE/PP), and a hydrocarbonbased resin such as polyimide, aramid, or polyvinylydenefluoride-hexafluoropropylene (PVdF-HFP), or glass fiber.

The thickness of the microporous (microporous membrane) separator cannotbe uniformly defined as it varies depending on use of application. Forexample, for an application in a secondary battery for operating a motorof an electric vehicle (EV), a hybrid electric vehicle (HEV), and a fuelcell vehicle (FCV), it is preferably 4 to 60 μm as a single layer or amultilayer. The fine pore diameter of the microporous (microporousmembrane) separator is preferably 1 μm or less at most (in general, thepore diameter is about several tens of nanometers). Furthermore, in thepresent example, a microporous separator was used.

As a non-woven separator, conventionally known ones such as cotton,rayon, acetate, nylon, and polyester; polyolefin such as PP and PE;polyimide and aramid are used either singly or as a mixture.Furthermore, it is sufficient that the thickness of the non-wovenseparator is the same as that of an electrolyte layer, and the thicknessthereof is preferably 5 to 200 μm, and particularly preferably 10 to 100μm.

[Positive Electrode Current Collecting Plate and Negative ElectrodeCurrent Collecting Plate]

The material for forming a current collecting plate (25, 27) is notparticularly limited, and a known highly conductive material which hasbeen conventionally used for a current collecting plate for a batterycan be used. Preferred examples of the material for forming a currentcollecting plate include metal materials such as aluminum, copper,titanium, nickel, stainless steel (SUS), and an alloy thereof. From theviewpoint of light weightiness, resistance to corrosion, and highconductivity, aluminum and copper are more preferable. Aluminum isparticularly preferable. Furthermore, the same material or a differentmaterial may be used for the positive electrode current collecting plate27 and the negative electrode current collecting plate 25.

<Positive Electrode Lead and Negative Electrode Lead>

Further, although it is not illustrated, the current collector 11 andthe current collecting plate (25, 27) may be electrically connected toeach other via a positive electrode lead or a negative electrode lead.The same material used for a lithium ion secondary battery of a relatedart can be also used as a material for forming the positive and negativeelectrode leads. Furthermore, a portion led from an outer casing ispreferably coated with a heat resistant and insulating thermallyshrunken tube or the like so that it has no influence on a product (forexample, an automobile component, in particular, an electronic device orthe like) according to electric leak after contact with peripheraldevices or wirings.

<Seal Part>

The seal part (insulation layer) has a function of preventing contactbetween the current collectors adjacent to each other and preventing ashort circuit caused at the end portion of the single battery layer. Thematerial constituting the seal part may be any materials as long as ithas an insulation property, a sealing property (sealing performance) toprevent the solid electrolyte from coming off and prevent permeation ofexternal moisture, heat resistance under battery operation temperatureand the like. Examples of the material include an acrylic resin, aurethane resin, an epoxy resin, a polyethylene resin, a polypropyleneresin, a polyimide resin, and rubber (ethylene-propylene-diene rubber:EPDM). Alternatively, an isocyanate adhesive, an acrylic resin adhesive,a cyanoacrylate adhesive, or the like may be used, and a hot-meltadhesive (urethane resin, polyamide resin, polyolefin resin) may also beused. Among these, from the viewpoint of corrosion resistance, chemicalresistance, ease of production (film-forming performance), economicalefficiency, and the like, a polyethylene resin or a polypropylene resinis preferably used as a constituent material of the insulation layer,and a resin containing an amorphous polypropylene resin as a maincomponent and obtained by copolymerizing ethylene, propylene, and buteneis preferably used.

[Battery Outer Casing]

As a battery outer casing, an envelope-shaped casing capable of coveringa power generating element as illustrated in FIG. 1, in which a laminatefilm 29 including aluminum is contained, may be used in addition to aknown metal can casing. As for the laminate film, a laminate film with athree-layered structure formed by laminating PP, aluminum, and nylon inthis order can be used, but is not limited thereto. From the viewpointof having higher output power and excellent cooling performance, and ofbeing suitably usable for a battery for a large instrument such as an EVor an HEV, a laminate film is desirable. In addition, since the grouppressure applied from outside to a power generating element can beeasily controlled and thus the thickness of an electrolyte solutionlayer can be easily controlled to a desired value, an aluminate laminateis more preferred for an outer casing.

In the bipolar secondary battery of this embodiment, when a positiveelectrode active material layer or a negative electrode active materiallayer is configured by using the above-described sheet-shaped electrode,the stress caused by expansion and shrinkage of an active material isalleviated even when an active material having a large battery capacityis used, and thus the cycle characteristics of the battery can beimproved. Therefore, the bipolar secondary battery of this embodiment issuitably used as a power source for operating an EV or an HEV.

FIG. 11 is a perspective view illustrating the appearance of a flatlithium ion secondary battery as a representative embodiment of asecondary battery.

As illustrated in FIG. 11, a flat lithium ion secondary battery 50 has aflat and rectangular shape, and from both sides, a positive electrodetab 58 and a negative electrode tab 59 are drawn to extract electricpower. A power generating element 57 is covered by a battery outercasing material (laminate film 52) of the lithium ion secondary battery50 with its periphery fused by heat. The power generating element 57 issealed in a state in which the positive electrode tab 58 and thenegative electrode tab 59 are led to the outside. Herein, the powergenerating element 57 corresponds to the power generating element 21 ofthe lithium ion secondary battery 10 illustrated in FIG. 1 as describedabove. In the power generating element 57, the positive electrode, theelectrolyte layer 17, and the negative electrode are laminated.According to a preferred embodiment, a plurality of them is laminated togive a power generating element.

Incidentally, the lithium ion secondary battery is not limited to a flatshape of laminate type. The winding type lithium ion secondary batterymay have a barrel shape or a flat and rectangular shape obtained bymodifying the barrel shape, and there is no particular limitation. As anouter casing material of the barrel shape, a laminate film may be used,or a barrel can (metal can) of a related art may be used, and thus thereis no particular limitation. Preferably, the power generating element isencased with an aluminum laminate film. The weight reduction may beachieved with such form.

Further, drawing of the tabs 58 and 59 illustrated in FIG. 11 is alsonot particularly limited. The positive electrode tab 58 and the negativeelectrode tab 59 may be drawn from the same side or each of the positiveelectrode tab 58 and the negative electrode tab 59 may be divided intoplural tabs and drawn from each side, thus there is no particularlimitation on the embodiment illustrated in FIG. 11. In addition, in awinding type lithium ion battery, it is also possible to form a terminalby using, for example, a barrel can (metal can) instead of a tab.

A typical electric vehicle has a battery storage space of about 170 L.Since a cell and an auxiliary machine such as a device for controllingcharging and discharging are stored in this space, storage spaceefficiency of a cell is generally about 50%. The cell loading efficiencyfor this space is a factor of determining the cruising distance of anelectric vehicle. As the size of a single cell decreases, the loadingefficiency is lowered, and thus it becomes impossible to maintain thecruising distance.

Therefore, in the present invention, the battery structure of whichpower generating element is covered with an outer casing preferably hasa large size. Specifically, the length of the short side of a laminatecell battery is preferably 100 mm or more. Such a large-sized batterycan be used for an automobile. Herein, the length of the short side ofthe laminate cell battery indicates the length of the shortest side. Theupper limit of the length of the short side is not particularly limited,but is generally 400 mm or less.

According to the market requirement, a typical electric vehicle needs tohave driving distance (cruising distance) of 100 km per single charge.Considering such a cruising distance, the volume energy density of abattery is preferably 157 Wh/L or more, and the rated capacity ispreferably 20 Wh or more.

Further, it is also possible to define the large size of a battery inview of a relation of battery area or battery capacity, from theviewpoint of a large-sized battery, which is different from a physicalsize of an electrode. For example, in the case of a flat and stack typelaminate battery, the problem of having lowered battery characteristics(cycle characteristics), which is caused by the collapse of the crystalstructure and the like accompanying expansion and shrinkage of an activematerial, may occur more easily in a battery having a value of a ratioof the battery area (projected area of a battery including a batteryouter casing) to the rated capacity is 5 cm²/Ah or more and having arated capacity of 3 Ah or more since the battery area per unit capacityis large. Therefore, the non-aqueous electrolyte secondary batteryaccording to this embodiment is preferably a large-sized battery asdescribed above from the viewpoint of having a larger merit obtainedfrom exhibition of the working effects of the present invention.Furthermore, an aspect ratio of a rectangular electrode is preferably 1to 3, and more preferably 1 to 2. Incidentally, the aspect ratio of theelectrode is defined by the longitudinal/transversal ratio of a positiveelectrode active material layer with a rectangular shape. When theaspect ratio is set to be in such a range, an advantage of having bothperformances required for a vehicle and loading space can be obtained.

As described above, according to an embodiment of the present invention,an active material of which surface is coated with a conductionassisting agent and a gel matrix polymer is used. Incidentally, in alithium ion secondary battery of a related art, a polymer compound suchas starch, polyvinylidene fluoride, polyvinyl alcohol, carboxylmethylcellulose, polyvinyl pyrrolidone, tetrafluoroethylene, styrene-butadienerubber, polyethylene, or polypropylene is used as a binder. However,according to an embodiment of the present invention, there is a meritthat a binder may not be used. Furthermore, according to gellation of anelectrolyte solution of a battery in which an electrode including aconductive member like carbon fiber is used, excellent ratecharacteristics of a battery are obtained, a crack or the like does notoccur on an electrode even with high thickness, and partial deformationof an electrode is not caused even when nonuniform pressure is applied.As such, excellent cycle durability of a battery can be obtained.

<Assembled Battery>

An assembled battery is formed by connecting plural batteries.Specifically, at least two of them are used in series, in parallel, orin series and parallel. According to arrangement in series or parallel,it is possible to freely adjust the capacity and voltage.

It is also possible to form a detachable small-size assembled battery byconnecting plural batteries in series or in parallel. Further, byconnecting again plural detachable small-size assembled batteries inseries or parallel, an assembled battery having high capacity and highoutput, which is suitable for a power source or an auxiliary powersource for operating a vehicle requiring a high volume energy densityand a high volume output density, can be formed. The number of theconnected batteries for producing an assembled battery or the number ofthe stacks of a small-size assembled battery for producing an assembledbattery with high capacity may be determined depending on the capacityor output of a battery of a vehicle (electric vehicle) on which thebattery is mounted.

<Vehicle>

The non-aqueous electrolyte secondary battery of the present inventioncan maintain discharge capacity even when it is used for a long periodof time, and thus has good cycle characteristics. Further, thenon-aqueous electrolyte secondary battery has a high volume energydensity. For use in a vehicle such as an electric vehicle, a hybridelectric vehicle, a fuel cell electric vehicle, or a hybrid fuel cellelectric vehicle, a long service life is required as well as highcapacity and large size compared to use for an electric and mobileelectronic device. Therefore, the non-aqueous electrolyte secondarybattery described above can be preferably used as a power source for avehicle, for example, as a power source for operating a vehicle or as anauxiliary power source for operating a vehicle.

Specifically, the battery or an assembled battery formed by combiningplural batteries can be mounted on a vehicle. According to the presentinvention, a battery with excellent long term reliability and outputcharacteristics, and a long service life can be formed, and thus, bymounting this battery, a plug-in hybrid electric vehicle with a long EVdriving distance or an electric vehicle with a long single-chargedriving distance can be achieved. This is because, when the battery oran assembled battery formed by combining plural batteries is used for,for example, an automobile such as a hybrid car, a fuel cell electriccar, and an electric car (including a two-wheel vehicle (motor bike) ora three-wheel vehicle in addition to all four-wheel vehicles (anautomobile, a truck, a commercial vehicle such as a bus, a compact car,or the like)), an automobile with a long service life and highreliability can be provided. However, the use is not limited to anautomobile, and it can be applied to various power sources of othertransportation means, for example, a moving object such as an electrictrain, and it can be also used as a power source for loading such as anUPS device.

EXAMPLES

Hereinbelow, detailed explanations are given using examples andcomparative examples, but the present invention is not limited only tothe following examples. Unless particularly described otherwise,“part(s)” means “part(s) by mass”.

<Preparation of Resin Solution for Coating>

To a four-necked flask equipped with a stirrer, were charged athermometer, a reflux condenser, a dropping funnel, and a nitrogen gasintroducing tube, 83 parts by mass of ethyl acetate and 17 parts by massof methanol, and the temperature was raised to 68° C.

Subsequently, a monomer blend solution obtained by blending 242.8 partsby mass of methacrylic acid, 97.1 parts by mass of methyl methacrylate,242.8 parts by mass of 2-ethylhexyl methacrylate, 52.1 parts by mass ofethyl acetate, and 10.7 parts by mass of methanol, and an initiatorsolution obtained by dissolving 0.263 part by mass of2,2′-azobis(2,4-dimethylvaleronitrile) in 34.2 parts by mass of ethylacetate were continuously added dropwise to the four-necked flask with adropping funnel while blowing nitrogen thereinto, under stirring over 4hours, to perform radical polymerization. After completion of dropwiseaddition, an initiator solution obtained by dissolving 0.583 part bymass of 2,2′-azobis(2,4-dimethylvaleronitrile) in 26 parts by mass ofethyl acetate was continuously added over 2 hours by using a droppingfunnel. Furthermore, the polymerization was continued at a boiling pointfor 4 hours. The solvent was removed, and 582 parts by mass of a resinwas obtained, then 1,360 parts by mass of isopropanol was added toobtain a resin solution for coating consisting of a vinyl resin with aresin concentration of 30% by weight.

<Preparation of Coated Positive Electrode Active Material>

96 Parts by weight of LiCoO₂ powder [manufactured by Nippon ChemicalIndustrial Co., Ltd., CELLSEED C-8G] were added to a universal mixer.After stirring at 150 rpm at room temperature (25° C.), a resin solutionfor coating (resin solid concentration of 30% by weight) was addeddropwise over 60 minutes to have the resin solid concentration of 2parts by weight followed by further stirring for 30 minutes.

Subsequently, in a stirring state, 2 parts by mass of acetylene black[manufactured by Denka Company Limited, Denka Black (registeredtrademark)] (average particle diameter (primary particle diameter):0.036 μm) was mixed in three divided times while stirring, and thetemperature was raised to 70° C. while keeping stirring for 30 minutes,then the pressure was reduced to 100 mmHg and held for 30 minutes.According to this operation, a coated positive electrode active materialwas obtained. Furthermore, the tensile elongation at break in asaturated liquid absorption state was found to be 50%. Furthermore, ifit is believed that the coated positive electrode active material has acore-shell structure, and the average particle diameter of LiCoO₂ powderwas 8 μm. Furthermore, shell thickness was 0.14 μm when simplecalculation is made for whole coating.

<Preparation of Electrolyte Solution 1>

By dissolving LiPF₆ at a ratio of 1 mol/L in a mixed solvent of ethylenecarbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1), anelectrolyte solution for lithium ion battery was prepared.

<Preparation of Electrolyte Solution 2>

To 100 parts by weight of electrolyte solution 1, were added 3.8 partsby weight of triethylene glycol diacrylate and 1 part by weight oftrimethylol propane triacrylate as a gelling agent followed by thoroughmixing. After that, 0.5 part by weight of t-butylperoxy pyvalate wasadded as a polymerization initiator followed by mixing. The mixtureobtained by mixing was kept in an incubator at 80° C. for thermalpolymerization for 2 hours. Conductivity for conductivity measurementwas prepared, and after temperature adjustment to 25° C., theconductivity was measured by an AC impedance method in view of themethod of measuring conduction rate of fine ceramic ion conductor of JISR 1661-2004. The conductivity was found to be 0.7 mS/cm.

<Preparation of Electrolyte Solution 3>

To 100 parts by weight of electrolyte solution 1, were added 7.6 partsby weight of triethylene glycol diacrylate and 2 parts by weight oftrimethylol propane triacrylate as a gelling agent followed by thoroughmixing. After that, 0.5 part by weight of t-butylperoxy pyvalate wasadded as a polymerization initiator followed by mixing. After performinggellation in the same manner as Example 1, a gel phase electrolyte forconductivity measurement was prepared, and the conductivity wasmeasured. The conductivity was found to be 0.3 mS/cm.

<Production of Positive Electrode Active Material Layer>

Carbon fiber [manufactured by Osaka Gas Chemicals Co., Ltd., DONACARBOMilled S-243, average fiber length: 500 μm, average fiber diameter: 13μm, electrical conductivity: 200 mS/cm] was prepared as a conductivemember.

1.75 Parts by weight of the above carbon fiber and 98.25 parts by weightof the coated positive electrode active material were mixed with 1000parts by weight of propylene carbonate to prepare a slurry.

On top of a glass filter of a separable flask of which suction part is aglass filter with ϕ70 mm, an aramid non-woven fabric (20 μm) wasapplied. The slurry dispersed in propylene carbonate was introducedthereto, and by applying pressure of 1.5 kg/cm² while simultaneouslyperforming suction filtering (depressurization), the coated positiveelectrode active material and carbon fiber were fixed on the aramidnon-woven fabric to produce a positive electrode active material layer.

The coating density of the positive electrode active material layer wasset at 120 mg/cm². The film thickness of the positive electrode activematerial layer was 500 μm at that time.

<Manufacture of Battery>

Reference Example 1

The positive electrode active material layer was moved such that thesurface of the positive electrode active material layer is on top of anAl current collector (i.e., surface of positive electrode activematerial layer is in contact with Al current collector), and as for thenegative electrode, Li metal foil adhered on a Cu current collector wasused.

The aramid non-woven fabric which has been obtained by supporting thecoated positive electrode active material and carbon fiber and placed onan Al current collector (i.e., coated positive electrode active materiallayer and aramid non-woven fabric are laminated in order on top of an Alcurrent collector) is added with electrolyte solution 1, and laminatedby inserting a PP separator between them (to a negative electrode)(i.e., configuration is such that Al current collector, coated positiveelectrode active material layer, aramid non-woven fabric, PP separator,Li metal foil, and Cu current collector are laminated in order, andaramid was also used as a separator in combination of polypropylene).

From the positive electrode Al current collector, an Al lead was drawn,and a Ni lead was drawn from the negative electrode Cu currentcollector. After encasing in an aluminum laminate pack (i.e., laminatedfilm), heat sealing under reduced pressure was carried out. The cell waspressed with two pieces of a SUS plate while being mediated by a rubbersheet.

Example 1

The cell was formed in the same manner as Reference Example 1 exceptthat electrolyte solution 1 is replaced with electrolyte solution 2.

Example 2

The cell was formed in the same manner as Reference Example 1 exceptthat electrolyte solution 1 is replaced with electrolyte solution 3.

Comparative Example 1

By using LiCoO₂ which has been used in the above and addingpolyvinylidene fluoride, and acetylene black, each in weight ratio of90:5:5, a slurry was prepared using N-methyl pyrrolidone as a solvent.The slurry was coated by an applicator on an Al current collector suchthat LiCoO₂ can have the coating density that is similar to that ofReference Example 1. After drying on a poplate, an electrode wasobtained. When the electrode was punched at ϕ60 mm, cracks haveoccurred.

<Evaluation of Charging and Discharging of Cell>

The cell was set in an incubator at 45° C. Then, the charge-dischargecycle durability test was carried out at the following conditions, andthe capacity retention rate after 50 cycles was summarized in Table 1.

The first two cycles include charging at CC-CV of 0.2 C to 4.2 V fortotal 8 hours and discharging at CC of 0.2 C to 2.5 V. After that, thecharging and discharging rate was charging for 3 hours at 0.5 C and CCdischarging at 0.5 C, and the capacity retention rate after 50 cyclesindicates the value relative to the third discharge capacity at 0.5 Ccharge-discharge conditions.

As it is understood from Table 1, when an active material is coated witha conduction assisting agent and a coating resin (i.e., gel matrixpolymer), a slurry is prepared by adding a conductive member (i.e.,carbon fiber), and a film is formed by depressurizing filtration methodor the like, a thick-film electrode with favorable reactivity can beprepared. Furthermore, when an electrolyte solution is gellated, abattery with excellent durability can be provided.

TABLE 1 Capacity retention rate (%) Reference Example 1 83 Example 1 91Example 2 93 Comparative Example 1 Positive electrode with the sameweight cannot be used due to cracks

REFERENCE SIGNS LIST

-   10 Bipolar secondary battery-   11 Current collector-   11 a Outermost current collector on positive electrode side-   11 b Outermost current collector on negative electrode side-   13 Positive electrode active material layer-   15 Negative electrode active material layer-   17 Electrolyte layer-   19 Single cell layer-   21 Power generating element-   23 Bipolar electrode-   25 Positive electrode current collecting plate-   27 Negative electrode current collecting plate-   29, 52 Laminate film-   31 Seal part-   58 Positive electrode tab-   59 Negative electrode tab-   14 Positive electrode active material-   24 Negative electrode active material-   111 First principal surface of positive electrode active material    layer-   121 Second principal surface of positive electrode active material    layer-   211 First principal surface of negative electrode active material    layer-   221 Second principal surface of negative electrode active material    layer-   131 Conductive fiber-   16 Conduction assisting agent-   151 Coating agent-   100 Positive electrode active material layer-   213 Conductive fiber-   214 Resin-   313 Resin-   60 Non-woven fabric-   62 Second principal surface of non-woven fabric-   70 Filter paper-   313 Filter paper-   470 Filter paper-   570 Plate-   110 Positive electrode active material layer-   50 Flat lithium ion secondary battery-   57 Power generating element

Incidentally, the present application is based on Japanese PatentApplication 2014-265522 which has been filed in Japan on Dec. 26, 2014,and the disclosures of which are incorporated herein by reference intheir entirety.

The invention claimed is:
 1. A non-aqueous electrolyte secondary batterycomprising a power generating element including: two electrodes havingdifferent polarities, each of the electrodes including an activematerial layer formed on a current collector; and an electrolyte layerpositioned between the electrodes, wherein the active material layer ofat least one of the electrodes contains an active material and aconductive member made from an electron conducting material, the activematerial layer has a first principal surface which comes into contactwith the electrolyte layer, and a second principal surface which comesinto contact with the current collector, at least a part of theconductive member forms a conductive path electrically connecting thefirst principal surface to the second principal surface, and theconductive path is in contact with the active material in a periphery ofthe conductive path, at least a part of a surface of the active materialis coated with a coating agent that includes a coating resin and aconduction assisting agent, an electrolyte solution contained in theelectrolyte layer or the electrodes is a gel phase electrolyte, thecoating resin has a tensile elongation at break of 10% or more in asaturated liquid absorption state, and the active material layer of atleast one of the electrodes does not contain a binder.
 2. Thenon-aqueous electrolyte secondary battery according to claim 1, whereina conductivity of the gel phase electrolyte is 0.1 mS/cm or more.
 3. Thenon-aqueous electrolyte secondary battery according to claim 1, furthercomprising: a matrix polymer configured to form the gel phaseelectrolyte, the matrix polymer including carboxylic acid ester as afunctional group.
 4. The non-aqueous electrolyte secondary batteryaccording to claim 1, wherein the coating resin is a urethane resin thatis obtained by reacting an active hydrogen component and an isocyanatecomponent.
 5. The non-aqueous electrolyte secondary battery according toclaim 1, wherein the coating resin is a polymer which has a vinylmonomer as an essential constitutional monomer and the vinyl monomerincludes a vinyl monomer having a carboxy group and a vinyl monomerrepresented by the following formula (1):CH₂═C(R¹)COOR²  (1) in the formula (1), R¹ is a hydrogen atom or amethyl group; and R² is a linear alkyl group having a carbon number of 1to 4 or a branched alkyl group having a carbon number of 4 to
 36. 6. Thenon-aqueous electrolyte secondary battery according to claim 1, furthercomprising: a matrix polymer configured to form the gel phaseelectrolyte, wherein the matrix polymer is obtained by adding a thermalpolymerization initiator to an electrolyte solution which contains amixture of at least a molecule having two polymerizable groups and amolecule having three polymerizable groups, and gelling the electrolytesolution by thermal polymerization.
 7. A method for manufacturing anon-aqueous electrolyte secondary battery having a power generatingelement including two electrodes having different polarities, the methodcomprising: forming an active material layer on a current collector; andpositioning an electrolyte layer between the electrodes, wherein theactive material layer of at least one of the electrodes contains anactive material and a conductive member made from an electron conductingmaterial, the active material layer has a first principal surface whichcomes into contact with the electrolyte layer, and a second principalsurface which comes into contact with the current collector, at least apart of the conductive member forms a conductive path electricallyconnecting the first principal surface to the second principal surface,and the conductive path is in contact with the active material in aperiphery of the conductive path, at least a part of a surface of theactive material is coated with a coating agent that includes a coatingresin and a conduction assisting agent, an electrolyte solutioncontained in the electrolyte layer or the electrodes is a gel phaseelectrolyte, the coating resin has a tensile elongation at break of 10%or more in a saturated liquid absorption state, and the active materiallayer of at least one of the electrodes does not contain a binder. 8.The manufacturing method according to claim 7, further comprisingforming the gel phase electrolyte by obtaining a matrix polymer byadding a thermal polymerization initiator to an electrolyte solutionwhich contains at least a molecule having two polymerizable groups and amolecule having three polymerizable groups, and gelling the electrolytesolution by thermal polymerization.
 9. The non-aqueous electrolytesecondary battery according to claim 1, wherein a thickness of theactive material layer of at least one of the electrodes is 200 μm ormore.
 10. The non-aqueous electrolyte secondary battery according toclaim 1, wherein the active material layer of each of the electrodesdoes not contain a binder.
 11. The manufacturing method according toclaim 7, wherein the active material layer of each of the electrodesdoes not contain a binder.